J. psych;&. Rex, Vol. 26, No. Printed in Great Britain.
ABNORMAL
1, PP. 69-75,
0
PLATELET
AND IMIPRAMINE PATRICIA Bernard
Baron Memorial
1992.
HANNAH,
5HYDROXYTRYPTAMINE
BINDING DIANA
Research Laboratories,
ADAMS,
IN POSTNATAL VIVETTE
Queen Charlotte’s
(Received 19 November
GLOVER
0022-3956/92 $5.00 + .oO 1992 Pergamon Press plc
UPTAKE DYSPHORIA
and M. SANDLER
and Chelsea Hospital,
London
W6 OXG, U.K.
1990; revised 16 July 1991)
Summary-Platelet “C-5-hydroxytryptamine (14C-5-HT) uptake, ‘H-imipramine binding and monoamine ohidase (MAO) activity were measured in women 5 days postpartum and compared with depression scores (Edinburgh Postnatal Depression Scale) at that time and 6 weeks later. Mean Km of 14C-5-HT uptake was significantly reduced in the group showing dysphoria at 5 days @ < 0.01). Mean Kd of 3H-imipramine binding was significantly increased in the group who later went on to become depressed at 6 weeks postpartum (p < 0.03). V,,, for “%-5-HT uptake, B,,, for ‘H-imipramine binding and MAO activity did not differ between depressed and non-depressed patients on either occasion. Although the observed changes manifested in a system known to be disturbed in other forms of depression, they were in affinity rather than B,, or V,,. Even though probably not of direct physiological significance, such results, if confirmed, together with other pointers in the literature, suggest biochemical abnormalities specific to the puerperal period.
Introduction psychosocial factors, such as poor marital relationships, may well be implicated in the development of postnatal mental illness (Kumar, 1982; O’Hara & Zekoski, 1988) a biochemical contribution is strongly suspected, although its nature is still unclear (Kumar & Robson, 1984; George & Sandler, 1988). Indeed, whether the incidence of depression is raised in the puerperium or exists as an entity distinct from non-puerperal mental illness remains controversial (Reich & Winokur, 1970; Brockington, 1982; O’Hara, 1987; Cooper, Campbell, Day, Kennerley, & Bond, 1988; O’Hara & Zekoski, 1988). It is customary to discriminate between the “blues”, a transient mood disturbance frequently observed in the first postpartum week, and postnatal depression which lasts much longer and is usually diagnosed a month or so after delivery (Stein, 1982; Kennerley & Gath, 1986). However, the topic is confused; it seems that, in at least a subgroup of women, there is an association between pronounced blues symptoms and later postnatal depression (Kennerley & Gath, 1986; Hapgood, Elkind, & Wright, 1988). We ourselves have noted a high correlation between Edinburgh Postnatal Depression Scale (EPDS) (Cox, Holden, & Sagovsky, 1987) scores at 5 days and 6 weeks postpartum (in preparation). It is plausible, then, to suppose that, in some cases, the blues and postnatal depression have a shared cause and manifest similar biochemical abnormalities. There is considerable evidence pointing to some abnormality of the 5-hydroxytryptamine (5HT) system in non-puerperal mental illness. In several studies using the blood platelet, the maximal rate of uptake (V,,,) of 5-HT was shown to be significantly reduced in subjects suffering from unipolar depression (Tuomisto & Tukiainen, 1976; Coppen, Swade, ALTHOUGH
69
70
PATRICIA HANNAH et al.
& Wood, 1978; Healy & Leonard, 1987). There are also reports of a reduction in number of binding sites (B,,,,,) for ‘H-imipramine (Briley, Langer, Raisman, Sechter, & Zarifian, 1980; Paul, Rehavi, Skolnick, Ballenger, & Goodwin, 1981; Healy & Leonard, 1987), although this finding has not been confirmed by others (Kanof, Coccaro, Johns, Siever, & Davies, 1987). The 3H-imipramine binding site, where tricyclic antidepressants bind to control 5-HT uptake, appears to be part of a complex common with the 5-HT uptake site (Healy & Leonard, 1987), although under separate control (Suranyi-Cadotte, Quirion, Nair, Lafaille, & Schwartz, 1985). Both high and low platelet monoamine oxidase (MAO) activity have been associated with anxiety and depression in several different psychiatric disorders (Snalling, Asbery, Edman, & Oreland, 1987). In the present study we have examined certain aspects of platelet 5-HT metabolism at 5 days postpartum and related them to EPDS score both at that time and 6 weeks later. Subjects
and Methods
Seventy-two subjects participated in the study. All were volunteers from postnatal wards at Queen Charlotte’s and Chelsea Hospital and had given birth to live babies by normal forceps-assisted vaginal delivery or by caesarian section. None had excessive blood loss at delivery nor were anaemic. Five days postpartum, a maximum of 35 ml blood was taken by forearm venepuncture. In some cases, because of patient discomfort, it was not practicable to obtain the full volume required to complete all biochemical tests. Patients were sampled between IO:30 a.m. and 11:30 a.m. to control for possible diurnal fluctuations in any of the variables. Platelet ‘C-5-HT uptake was measured by a modification of the method of Coppen, Swade, and Wood (1978). Blood, collected into 5% EDTA (20:1), was centrifuged (32Og, 5 min) to yield platelet-rich plasma (PRP). Uptake was determined by adding 14C-5-HT (6 concentrations, 0.25-4.0 PM; 50 ~1) to PRP (100 ~1) diluted in phosphate buffer, pH 7.5 (850 PI), incubating the mixture at 37°C in a shaking water bath for 5 min. After terminating uptake with formaldehyde (2.25%), isolated platelets were lysed with 8 M urea (400 ~1). Non-specific uptake was determined simultaneously at 0°C. V,,,,, and Michaelis-Menten constant (Km) were calculated from Lineweaver-Burk plots. The ‘H-imipramine binding assay was based on the method of Geaney et al. (1984). An intact platelet preparation (200 11) was incubated with JH-imipramine (6 concentrations, 0.3-3.0 nM; 25 ~1) and saline buffer, pH 7.4 (25 PI), for 1 hr at O”C, the platelets then being isolated by vacuum filtration using Whatman GF/F filters. Non-specific binding was measured in the presence of desipramine (10 PM; 25 ~1). This was found to be sufficient to displace specific binding from intact platelets. B,,,;,, and dissociation constant (Kd) were calculated from Scatchard plots. MAO activity was measured by a method based on that of Reveley, Glover, Sandler, & Coopen (1981), using 143 PM ‘“C-tyramine as substrate, and extracting the reaction product into toluene/ethyl acetate 1: 1. Platelet counts were determined by automated counting (Sysmex C-780) and protein concentration by the method of Lowry, Rosebrough, Farr, & Randall (195 1). Plasma sodium and potassium concentrations were measured by indirect ion-selective electrode (Beckman System E2A) and calcium and urea by standard calorimetric methods (Coulter CPA).
5-HT KINETICS IN POSTNATAL DYSPHORIA
11
Mood was assessed on the day of blood sampling using the EPDS (Cox et al., 1987), a lo-item self-rating questionnaire with a total score range of 0 to 30, originally designed to detect postnatal depression six weeks postpartum. It avoids the use of somatic symptoms, included in many other scales, as they could be caused by normal physiological changes associated with childbearing. Six weeks after delivery, the subjects were sent a second copy of the EPDS to complete and return by mail. Repeat blood sampling was not practicable at this stage as the patients had returned to their own homes. Patients were classified at both 5 days and 6 weeks postpartum as scoring 2 10 or < 10 on the EPDS scale. The original validation of the scale showed that at 6 weeks postpartum, this cut-off distinguishes borderline and probable cases of postnatal depression from non-cases (Cox et al., 1987). Therefore, the novel use of the EPDS at 5 days postpartum and the inclusion of relatively mild cases at 6 weeks may make it more appropriate to relate a score of 10 or more on either occasion to postnatal dysphoria rather than depression. Results The results are summarized in Table 1. The mean age of both depressed and nondepressed groups was 30 years in all the groups analysed. As the data from nondepressed subjects showed a non-parametric distribution, a log transformation was used before statistical analysis by 2-tailed Student’s t-test. Table 1 Platelei 5-HT uptake, ‘H-imipramine taken at 5 days postpartum; relation
binding and MAO activity (mean and 95% confidence to EPDS score at 5 days or 6 weeks postpartum
2 10 n= 19 0.29 (0.25-0.30)* 110 (93-131)
< 10 n=44 0.37 (0.33-0.41) 126 (112-142)
6 Week 2 10 < 10 n=lS n=40 0.32 (0.27-0.37) 0.36 (0.32-0.40) 120 (102-140) 116 (100-134)
n= 15 0.92 (0.69-1.24) 138 (107-179)
n=40 0.80 (0.66-0.96) 145 (124-170)
n=ll 1.15 (0.84-1.56)t 155 (116-207)
n=39 0.74 (0.61-0.89) 144 (124-168)
n=20 15.2 (13.4-17.3)
n=52 15.3 (13.9-16.9)
n= 15 16.8 (14.2-19.9)
n=47 15.1 (13.7-16.7)
5 Day EPDS 5-HT uptake Km V Ill&x (pmo1/108 platelets/5
min)
3H-imipramine binding Kd B lllil’c (fmol/lO* platelets) MAO activity nmol product/mg
limits) in platelets
protein/30
min
2.tailed Student’s t-test after log transformation of data. *At 5 days-different from EPDS < 10, p < 0.01. tAt 6 weeks-different from EPDS < 10, p < 0.03.
The Km for platelet ‘%Z-5-HT uptake was significantly reduced in the group with high EPDS score at 5 days postpartum @ < 0.01). Although a similar trend was shown for those who became depressed later, at 6 weeks postpartum, significance was not achieved. V,,, did not differ between any of the groups. The Kd for 3H-imipramine binding showed a rise which failed to reach significance in depressed compared with non-depressed subjects
72
PATRICIA HANNAH et al
at 5 days postpartum and was significantly raised in the group depressed at 6 weeks No differences were found in platelet MAO ti < 0.03). B,,,, was similar throughout. activity, nor were there any significant differences in depression score if the upper or lower 15% of MAO activity values were compared with the middle 70%. Plasma sodium, potassium, calcium and urea concentrations were very similar and did not vary significantly between the different groups shown in Table 1. Patients in depressed and nondepressed groups were in receipt of very similar drugs. If those taking only analgesic medication are considered, the difference in Km for 5-HT uptake is still clearly shown i.e. Km (mean&SD) when EPDS measured at 5 days: 2 10, 0.28 =0.5 PM, n = 7; < 10, 0.42+0.17 yM, n =21 @ < 0.03). Mean Kd values for )Himipramine binding in these “analgesic-only” patients are also similar to those of the whole group although the differences were no longer statistically significant i.e. Kd (mean f SD) when EPDS measured at 6 weeks: 2 10, 1.13 ho.70 nM, n =6; < 10,0.76&0.47 nM, n = 14. A two-way analysis of variance showed no significant interaction between caesarian section delivery and either Km for 5-HT uptake or Kd for ‘H-imipramine binding, in relation to depression score at either 5 days or 6 weeks postpartum. Discussion This study presents evidence of disturbances in the substrate affinity of platelet systems involved in 5-HT control, detectable in blood samples drawn 5 days postpartum, both in women depressed at that time, and in those (an overlapping, but different group) who went on to develop some features of longer term postnatal depression. It is of interest that the changes were not in V,, for 5-HT uptake or B,, for )H-imipramine binding, as had been noted in the non-puerperal illness (see Introduction). However, outside the postpartum period, there are sporadic reports in the literature of changes in affinity e.g. diurnal variation in Km for 5-HT uptake (Arora, Kregel, & Meltzer, 1984; Jerushalmy et al., 1988). A hypothesis of variable receptor affinity, based on studies of the az-adrenoreceptor, has recently been proposed (Bevan, Bevan, & Shreeve, 1989). There are also pointers in the literature to changes in receptor affinity in the immediate postpartum period. An increase in Kd for 3H-imipramine binding 5-7 days postpartum compared with other antenatal and postnatal time-points has been reported by Katona et al. (1985). In addition, the Kd of platelet ‘H-yohimbine binding has been reported to increase postnatally (Metz et al., 1983). However, it should be noted that the changes in affinity observed here are small, less than one order of magnitude, and thus may well not be of direct physiological significance. Their potential interest lies in the fact that they suggest the possibility ol generalised membrane abnormalities or abnormal circulating factors occurring in the immediate postpartum period. It would have been desirable to have obtained a second blood sample from these patients at 6 weeks postpartum but this was not practicable in the present study. It is of interest that Butler and Leonard (1986), who did examine such a group of severely depressed postpartum women, found a significant decrease in V,,,, of 5-HT uptake with no change in Km. It is possible that the changes we have observed are confined to the very early puerperium and that, later, the biochemical correlates of postnatal depression are the same as those of depression occurring at other times.
S-HT KINETICS IN POSTNATAL DYSPHORIA
13
A massive fall in circulating oestrogen and progesterone occurs at parturition. These hormones are known to act on central and peripheral monoamine centres (e.g., Ehrenkranz, 1976; Biegon, Reches, Snyder, & McEwen, 1983). It has been suggested that changes in postpartum mood are linked with this fall although, as yet, there is no direct evidence for this (Nott, Franklin, Armitage, & Gelder, 1976; Kuevi et al., 1983). In addition, there is little experimental evidence of the Km for 5-HT uptake or Kd for 3H-imipramine binding varying with such hormonal changes. Castren and Tuomisto (1983) failed to find differences in Km or V,,, for 5-HT uptake between women in late pregnancy and those during the first 9 days after delivery, despite vast differences in hormone balance. Even though no consistent changes have been found in the Km of 5-HT uptake during different phases of the menstrual cycle (Taylor, Matthew, & Weinmann, 1984; Tam, Chan, & Lee, 1985; Ashby, Carr, Cook, Steptoe, & Franks, 1988), it is of interest that a significant correlation has been noted between menstrual behavioural changes and this variable (Taylor et al., 1984). 3H-Imipramine binding does not appear to vary through the menstrual cycle (Stowell, McIntosh, Cooke, & Ellis, 1988). There are several possible technical factors that can affect the measurement of imipramine binding. In this study, we employed intact platelets rather than a membrane preparation, and this should eliminate possible variations due to different amounts of intracellular protein. However, studies using both methods have found a reduced B,,, in depressed patients compared with controls (Meltzer & Arora, 1991). We also used 10 PM desipramine to define nonspecific binding and there is now evidence that lo-100 FM desipramine displaces 3H-imipramine binding from more than one site. A single saturable high affinity 3H-imipramine binding site has been defined in platelets (Marcusson & Tiger, 1988) and brain (Arora & Meltzer, 1989), using 5-HT as displacing agent. However, there is no evidence that this site is reduced in depression. It is known that changes in Km or Kd are extremely sensitive to experimental conditions and to drug or metabolite residues in the platelets. 5-HT accumulation by the platelet is, for example, highly dependent on the presence of sodium ions; sodium-free medium abolishes uptake, whereas the addition of sodium stimulates it, causing a reduction in Km (Sneddon, 1983). The affinity of imipramine for its binding site is also dependent on a sodium ion contribution (Abbott, Briley, Langer, & Setter, 1982). In this present study, however, the sodium concentration in the incubation medium was controlled and there was no difference in plasma sodium (or any other analyte measured) between depressed and non-depressed groups. However, even though there were no obvious drug effects (in that “analgesic only” patients showed similar results to the whole group), it would seem necessary to confirm this finding in a larger group of drug-free patients. It is unlikely that drug abuse was a confounding factor in this group of women; none of the recruits were reported as abusers during their pregnancy. There have been few biochemical studies to date differentiating women with postpartum dysphoria from others. One finding, which may be relevant to the current observations, is that free plasma tryptophan is low in women depressed on the sixth day postpartum (Stein, Milton, Bebbington, Wood, & Coppen, 1976; Handley, Dunn, Baker, Cockshott, & Gould, 1977). Such depletion might lead directly to changes in processes governing 5-HT metabolism because tryptophan is a precursor of 5-HT or indirectly
74
PATRICIA HANNAH et al.
if, for example, tryptophan were the precursor of a competitive inhibitor of 5-HT uptake. The present study, then, has found evidence for a reduction in Km of 5-HT uptake in platelets sampled 5 days postpartum in women who scored L 10 on the EPDS at this time, and an increase in Kd for imipramine binding in these platelets in patients who went on to score 2 10 at 6 weeks. If confirmed, these findings suggest that the biochemistry of mood changes occurring in the immediate postpartum period is somewhat different from that occurring at other times of life. References Abbott, W., Briley, M. S., Langer, S. Z., & Setter, M. (1982). Sodium shift of the inhibition of j3Hjimipramine binding by 5-HT and 5-HT uptake blockers but not by tricyclic antidepressants. &ins/t Journal of Pharmacology, 76, 29%‘. Arora, R. C., Kregel, L., & Meltzer, H. Y. (1984). Circadian rhythm of serotonin uptake in the blood platelets of normal controls. Biological Psychiatry, 19, 1579-1584. Arora, R. C., & Meltzer, H. Y. (1989). Serotonergic measures in the brains of suicide victims: 5-HT, binding sites in the frontal cortex of suicide victims and control subjects. American Journal of Psychiatry, 146, 730-736. Ashby, C. R., Carr, L. A., Cook, C. L., Steptoe, N. M., &Franks, D. D. (1988). Alteration of platelet serotonergic mechanisms and monoamine oxidase activity in premenstrual syndrome. Biologica/ fsychiutrv, 24, 225-233. Bevan, J. A., Bevan, R. D., & Shreeve, S. M. (1989). Variable receptor affinity hypothesis. Federation ofAmerican Societies for Experimental Biology Journul, 3, 1696- 1704. Biegon, A., Reches, A., Snyder, S. L., & McEwen, B. S. (1983). Serotonergic and noradrenergic receptors in the rat bain: modulation by chronic exposure to ovarian hormones. Life Sciences, 32, 2015-2021. Briley, M. S., Langer, S. Z., Raisman, R., Sechter, D., & Zarifian, E. (1980). 3H-Imipramine binding sites are decreased in platelets of untreated depressed patients. Science, 209, 303-305. Brockington, I. (1982). Puerperal psychosis. In: Brockington, 1. F. and Kumar, R. (Eds), Motherhood and mental illness. (pp. 37-70). London: Academic Press. Butler, J., & Leonard, B. E. (1986). Postpartum depression and the effect of nomifensine treatment. Inrernai/onu/ Clinical Psychopharmacology, 1, 244-252. Castren, E., & Tuomisto, J. (1983). Influence of the hormonal balance of late pregnancy on the active uptake of 5-hydroxytryptamine by human blood platelets. Medical Biology, 61, 168-171. Cox, J. L., Holden, J. M., & Sagovsky, R. (1987). Detection of postnatal depression: development of the IO-item Edinburgh Postnatal Depression Scale. British Journal of Psychiatry, 150, 782-786. Cooper, P. J., Campbell, E. A., Day, A., Kennerley, H., &Bond, A. (1988). Non-psychotic psychiatric disorder after childbirth: a prospective study of prevalence, incidence, course and nature. British Journu/ of Psychiatry, 152, 799-806. Coppen, A. L., Swade, C., &Wood, K. (1978). Platelet 5.hydroxytryptamine accumulation in depressive illness. Clintcu Chimicu Aclu, 87, 165-168. Ehrenkrana, J. R. L. (1976). Effects of sex steroids on serotonin uptake in blood platelets. Actu Endocrinologicu, 83, 420-428. Geaney, D. P., Rutterford, M. G., Elliott, J. M., Schachtcr, M., Peer, K. M. S., & Grahame-Smith, D. G. (1984). Decreased platelet (‘H)-imipramine binding sites in classical migraine. Journul ofNeurology, ,Veurosurgery, and Psychiatry, 47, 720-723. George, A., & Sandler, M. (1988). Endocrine and biochemical studies in puerperal mental disorders. In: I. F. Brockington and R. Kumar (Eds) Motherhood and Mental l//ness 2. (pp. 78-l 12). London: Academic Press. Handley, S. L., Dunn, T. L., Baker, J. M., Cockshott, C., & Gould, S. (1977). Mood changes in the puerperium and plasma tryptophan and cortisol. British Medical Journal, 2, 18-22. Hapgood, C. C., Elkind, G. S., & Wright, J. J. (1988). Maternity blues: phenomena and relationship to later postpartum depression. Australian and New Zealand Journal of Psychiarry, 22, 299-306. Healy, D., & Leonard, B. E. (1987). Monoamine transport in depression: kinetics and dynamics. Journal of Affective Disorders, 12. 91- 103 Jerushalmy, Z., Modai, I., Chachkes, O., Mark, M., Valewski, A., Chachkes, M., & Tyano, S. (1988). Kinetic values of active serotonin transport by platelets of bipolar, unipolar and schirophrcnic patients at 2 and 8am. Neuropsychobio/og_v, 20, 57-61.
5.HT KINETICS IN POSTNATAL DYSPHORIA
75
Kanof, P. D., Coccaro, E. F., Johns, C. A., Siever, L. J., & Davies, K. L. (1987). Platelet (3H-imipramine) binding in psychiatric disorders. Biological Psychiatry, 22, 278-286. Katona, C. L. E., Theodorou, A. E., Missouris, C. G., Bourke, M. P., Horton, R. W., Moncrieff, D., Paykel, E. S., & Kelly, J. S. (1985). Platelet 3H-imipramine binding in pregnancy and the puerperium. Psychiatry Research, 14, 33-37. Kennerley, H., & Gath, D. (1986). Maternity blues reassessed. Psychiatry Develoment, 1, 1-17. Kuevi, V., Carson, R., Dixon, A. F., Everard, D. M., Hall, J. M., Hole, D., Whitehead, S. A., Wilson, C. A., & Wise, J. C. (1983). Plasma amine and hormone changes in post-partum blues. ClinicalEndocrinology, 19, 39-46. Kumar, R. (1982). Neurotic disorders in childbearing women. In Brockington, I. F. & Kumar, R. (Eds) Motherhood and mental illness (pp. 71-l 18). London: Academic Press. Kumar, R., & Robson, K. M. (1984). A prospective study of emotional disorders in childbearing women. British Journal of Psychiatry, 144, 35-47. Lowry, 0. H., Rosebrough, N. J., Farr, A. L., & Randall, R. J. (1951). Protein measurement with the Folin phenol reagent. Journal of Biological Chemistry, 193, 265-275. Marcusson, J. O., & Tiger, G. (1988). [3H]lmipramine binding of protein nature in human platelets: Inhibition by 5-hydroxytryptamine and 5-hydroxytryptamine uptake inhibitors. Journal of Neurochemistry, 50, 1032-1036. Metz, A., Cowen, P. J., Gelder, M. G., Stump, K., Elliott, J. M., & Grahame-Smith, D. G. (1983). Changes in platelet ol-adrenoceptor binding post-partum: possible relation to maternity blues. Lancer, i, 495-498. Meltzer, H. Y., & Arora, R. C. (1991). Platelet serotonin studies in affective disorders: evidence for a serotonergic abnormality? In: Sandler, M., Coppen, A. and Harnett, S. (Eds), S-Hydroxytryptamine inpsychiatry-aspectrum of ideas (pp. 50-89). Oxford: Oxford University Press. Nott, P. N., Franklin, M., Armitage, C., & Gelder, M. G. (1976). Hormonal changes in post-partum blues. Clinical Endocrinology, 19, 39-46. O’Hara, M. W. (1987). Post-partum ‘blues’, depression, and psychosis: a review. Journal of Psychosomatic Obstetrics & Gynecology, 7, 205-227. O’Hara, M. W., & Zekoski, E. M. (1988). Postpartum depression: A comprehensive review. In I. F. Brockington, R. Kumar (Eds), Motherhood and mental illness 2 (pp. 17-63). London: Academic Press. Paul, S. M., Rehavi, M., Skolnick, P., Ballenger, J. C., &Goodwin, F. K. (1981). Depressed patients have decreased binding of tritiated imipramine to platelet serotonin transporter. Archives of General Psychiatry, 38, 1315-1317. Reich, T., & Winokur, G. (1970). Postpartum psychoses in patients with manic depressive disease. Journal of Nervous and Mental Disorders, 151, 66-68. Reveley, M. A., Glover, V., Sandler, M., & Coppen, A. (1981). Increased platelet monoamine oxidase activity in affective disorders. Psychopharmacology, 13, 257-260. Snalling, D., Asberg, M., Edman, G., & Oreland, L. (1987). Markers for vulnerability to psychopathology: Temperament traits associated with platelet MAO activity. Acta Psychiatrica Scandinavica, 76, 172-182. Sneddon, J. M. (1983). Blood platelets as a model for monoamine-containing neurones. Progress in Neurobiology, 1, 151-198. Stein, G. (1982). The maternity blues. In Brockington, I. F., and Kumar, F. (Eds). Motherhood and mental illness (pp. 119-154). London: Academic Press. Stein, G. S., Milton, F., Bebbington, P., Wood, K., & Coppen, A. (1976). Relationship between mood disturbances and free and total plasma tryptophan in post-partum women. British Medical Journal, 2, 457-459. Stowell, L. I., McIntosh, C. J., Cooke, R., &Ellis, P. M. (1988). Adrenoceptor and imipramine receptor binding during the menstrual cycle. Acta Psychiatrica Scandinavica, 78, 366-368. Suranyi-Cadotte, H. E., Quirion, R., Nair, N. P. V., Lafaille, F., & Schwarz, G. (1985). lmipramine treatment differentially affects platelet ‘H-imipramine binding and serotonin uptake in depressed patients. Life Sciences, 36, 795-799. Tam, W. Y. K., Chan, M-Y., & Lee, P. H. K. (1985). The menstrual cycle and platelet 5.HT uptake. Psychosomatic Medicine, 47, 352-362. Taylor, 0. L., Matthew, R. J., & Weinman, M. L. (1984). Serotonin levels and platelet uptake during premenstrual tension. Neuropsychobiology, 12, 16-18. Tuomisto, J., & Tukiainen, E. (1976). Decreased uptake of S-hydroxytryptamine in blood platelets from depressed patients. Nature, 262, 596-598.
ABNORMAL
1, PP. 69-75,
0
PLATELET
AND IMIPRAMINE PATRICIA Bernard
Baron Memorial
1992.
HANNAH,
5HYDROXYTRYPTAMINE
BINDING DIANA
Research Laboratories,
ADAMS,
IN POSTNATAL VIVETTE
Queen Charlotte’s
(Received 19 November
GLOVER
0022-3956/92 $5.00 + .oO 1992 Pergamon Press plc
UPTAKE DYSPHORIA
and M. SANDLER
and Chelsea Hospital,
London
W6 OXG, U.K.
1990; revised 16 July 1991)
Summary-Platelet “C-5-hydroxytryptamine (14C-5-HT) uptake, ‘H-imipramine binding and monoamine ohidase (MAO) activity were measured in women 5 days postpartum and compared with depression scores (Edinburgh Postnatal Depression Scale) at that time and 6 weeks later. Mean Km of 14C-5-HT uptake was significantly reduced in the group showing dysphoria at 5 days @ < 0.01). Mean Kd of 3H-imipramine binding was significantly increased in the group who later went on to become depressed at 6 weeks postpartum (p < 0.03). V,,, for “%-5-HT uptake, B,,, for ‘H-imipramine binding and MAO activity did not differ between depressed and non-depressed patients on either occasion. Although the observed changes manifested in a system known to be disturbed in other forms of depression, they were in affinity rather than B,, or V,,. Even though probably not of direct physiological significance, such results, if confirmed, together with other pointers in the literature, suggest biochemical abnormalities specific to the puerperal period.
Introduction psychosocial factors, such as poor marital relationships, may well be implicated in the development of postnatal mental illness (Kumar, 1982; O’Hara & Zekoski, 1988) a biochemical contribution is strongly suspected, although its nature is still unclear (Kumar & Robson, 1984; George & Sandler, 1988). Indeed, whether the incidence of depression is raised in the puerperium or exists as an entity distinct from non-puerperal mental illness remains controversial (Reich & Winokur, 1970; Brockington, 1982; O’Hara, 1987; Cooper, Campbell, Day, Kennerley, & Bond, 1988; O’Hara & Zekoski, 1988). It is customary to discriminate between the “blues”, a transient mood disturbance frequently observed in the first postpartum week, and postnatal depression which lasts much longer and is usually diagnosed a month or so after delivery (Stein, 1982; Kennerley & Gath, 1986). However, the topic is confused; it seems that, in at least a subgroup of women, there is an association between pronounced blues symptoms and later postnatal depression (Kennerley & Gath, 1986; Hapgood, Elkind, & Wright, 1988). We ourselves have noted a high correlation between Edinburgh Postnatal Depression Scale (EPDS) (Cox, Holden, & Sagovsky, 1987) scores at 5 days and 6 weeks postpartum (in preparation). It is plausible, then, to suppose that, in some cases, the blues and postnatal depression have a shared cause and manifest similar biochemical abnormalities. There is considerable evidence pointing to some abnormality of the 5-hydroxytryptamine (5HT) system in non-puerperal mental illness. In several studies using the blood platelet, the maximal rate of uptake (V,,,) of 5-HT was shown to be significantly reduced in subjects suffering from unipolar depression (Tuomisto & Tukiainen, 1976; Coppen, Swade, ALTHOUGH
69
70
PATRICIA HANNAH et al.
& Wood, 1978; Healy & Leonard, 1987). There are also reports of a reduction in number of binding sites (B,,,,,) for ‘H-imipramine (Briley, Langer, Raisman, Sechter, & Zarifian, 1980; Paul, Rehavi, Skolnick, Ballenger, & Goodwin, 1981; Healy & Leonard, 1987), although this finding has not been confirmed by others (Kanof, Coccaro, Johns, Siever, & Davies, 1987). The 3H-imipramine binding site, where tricyclic antidepressants bind to control 5-HT uptake, appears to be part of a complex common with the 5-HT uptake site (Healy & Leonard, 1987), although under separate control (Suranyi-Cadotte, Quirion, Nair, Lafaille, & Schwartz, 1985). Both high and low platelet monoamine oxidase (MAO) activity have been associated with anxiety and depression in several different psychiatric disorders (Snalling, Asbery, Edman, & Oreland, 1987). In the present study we have examined certain aspects of platelet 5-HT metabolism at 5 days postpartum and related them to EPDS score both at that time and 6 weeks later. Subjects
and Methods
Seventy-two subjects participated in the study. All were volunteers from postnatal wards at Queen Charlotte’s and Chelsea Hospital and had given birth to live babies by normal forceps-assisted vaginal delivery or by caesarian section. None had excessive blood loss at delivery nor were anaemic. Five days postpartum, a maximum of 35 ml blood was taken by forearm venepuncture. In some cases, because of patient discomfort, it was not practicable to obtain the full volume required to complete all biochemical tests. Patients were sampled between IO:30 a.m. and 11:30 a.m. to control for possible diurnal fluctuations in any of the variables. Platelet ‘C-5-HT uptake was measured by a modification of the method of Coppen, Swade, and Wood (1978). Blood, collected into 5% EDTA (20:1), was centrifuged (32Og, 5 min) to yield platelet-rich plasma (PRP). Uptake was determined by adding 14C-5-HT (6 concentrations, 0.25-4.0 PM; 50 ~1) to PRP (100 ~1) diluted in phosphate buffer, pH 7.5 (850 PI), incubating the mixture at 37°C in a shaking water bath for 5 min. After terminating uptake with formaldehyde (2.25%), isolated platelets were lysed with 8 M urea (400 ~1). Non-specific uptake was determined simultaneously at 0°C. V,,,,, and Michaelis-Menten constant (Km) were calculated from Lineweaver-Burk plots. The ‘H-imipramine binding assay was based on the method of Geaney et al. (1984). An intact platelet preparation (200 11) was incubated with JH-imipramine (6 concentrations, 0.3-3.0 nM; 25 ~1) and saline buffer, pH 7.4 (25 PI), for 1 hr at O”C, the platelets then being isolated by vacuum filtration using Whatman GF/F filters. Non-specific binding was measured in the presence of desipramine (10 PM; 25 ~1). This was found to be sufficient to displace specific binding from intact platelets. B,,,;,, and dissociation constant (Kd) were calculated from Scatchard plots. MAO activity was measured by a method based on that of Reveley, Glover, Sandler, & Coopen (1981), using 143 PM ‘“C-tyramine as substrate, and extracting the reaction product into toluene/ethyl acetate 1: 1. Platelet counts were determined by automated counting (Sysmex C-780) and protein concentration by the method of Lowry, Rosebrough, Farr, & Randall (195 1). Plasma sodium and potassium concentrations were measured by indirect ion-selective electrode (Beckman System E2A) and calcium and urea by standard calorimetric methods (Coulter CPA).
5-HT KINETICS IN POSTNATAL DYSPHORIA
11
Mood was assessed on the day of blood sampling using the EPDS (Cox et al., 1987), a lo-item self-rating questionnaire with a total score range of 0 to 30, originally designed to detect postnatal depression six weeks postpartum. It avoids the use of somatic symptoms, included in many other scales, as they could be caused by normal physiological changes associated with childbearing. Six weeks after delivery, the subjects were sent a second copy of the EPDS to complete and return by mail. Repeat blood sampling was not practicable at this stage as the patients had returned to their own homes. Patients were classified at both 5 days and 6 weeks postpartum as scoring 2 10 or < 10 on the EPDS scale. The original validation of the scale showed that at 6 weeks postpartum, this cut-off distinguishes borderline and probable cases of postnatal depression from non-cases (Cox et al., 1987). Therefore, the novel use of the EPDS at 5 days postpartum and the inclusion of relatively mild cases at 6 weeks may make it more appropriate to relate a score of 10 or more on either occasion to postnatal dysphoria rather than depression. Results The results are summarized in Table 1. The mean age of both depressed and nondepressed groups was 30 years in all the groups analysed. As the data from nondepressed subjects showed a non-parametric distribution, a log transformation was used before statistical analysis by 2-tailed Student’s t-test. Table 1 Platelei 5-HT uptake, ‘H-imipramine taken at 5 days postpartum; relation
binding and MAO activity (mean and 95% confidence to EPDS score at 5 days or 6 weeks postpartum
2 10 n= 19 0.29 (0.25-0.30)* 110 (93-131)
< 10 n=44 0.37 (0.33-0.41) 126 (112-142)
6 Week 2 10 < 10 n=lS n=40 0.32 (0.27-0.37) 0.36 (0.32-0.40) 120 (102-140) 116 (100-134)
n= 15 0.92 (0.69-1.24) 138 (107-179)
n=40 0.80 (0.66-0.96) 145 (124-170)
n=ll 1.15 (0.84-1.56)t 155 (116-207)
n=39 0.74 (0.61-0.89) 144 (124-168)
n=20 15.2 (13.4-17.3)
n=52 15.3 (13.9-16.9)
n= 15 16.8 (14.2-19.9)
n=47 15.1 (13.7-16.7)
5 Day EPDS 5-HT uptake Km V Ill&x (pmo1/108 platelets/5
min)
3H-imipramine binding Kd B lllil’c (fmol/lO* platelets) MAO activity nmol product/mg
limits) in platelets
protein/30
min
2.tailed Student’s t-test after log transformation of data. *At 5 days-different from EPDS < 10, p < 0.01. tAt 6 weeks-different from EPDS < 10, p < 0.03.
The Km for platelet ‘%Z-5-HT uptake was significantly reduced in the group with high EPDS score at 5 days postpartum @ < 0.01). Although a similar trend was shown for those who became depressed later, at 6 weeks postpartum, significance was not achieved. V,,, did not differ between any of the groups. The Kd for 3H-imipramine binding showed a rise which failed to reach significance in depressed compared with non-depressed subjects
72
PATRICIA HANNAH et al
at 5 days postpartum and was significantly raised in the group depressed at 6 weeks No differences were found in platelet MAO ti < 0.03). B,,,, was similar throughout. activity, nor were there any significant differences in depression score if the upper or lower 15% of MAO activity values were compared with the middle 70%. Plasma sodium, potassium, calcium and urea concentrations were very similar and did not vary significantly between the different groups shown in Table 1. Patients in depressed and nondepressed groups were in receipt of very similar drugs. If those taking only analgesic medication are considered, the difference in Km for 5-HT uptake is still clearly shown i.e. Km (mean&SD) when EPDS measured at 5 days: 2 10, 0.28 =0.5 PM, n = 7; < 10, 0.42+0.17 yM, n =21 @ < 0.03). Mean Kd values for )Himipramine binding in these “analgesic-only” patients are also similar to those of the whole group although the differences were no longer statistically significant i.e. Kd (mean f SD) when EPDS measured at 6 weeks: 2 10, 1.13 ho.70 nM, n =6; < 10,0.76&0.47 nM, n = 14. A two-way analysis of variance showed no significant interaction between caesarian section delivery and either Km for 5-HT uptake or Kd for ‘H-imipramine binding, in relation to depression score at either 5 days or 6 weeks postpartum. Discussion This study presents evidence of disturbances in the substrate affinity of platelet systems involved in 5-HT control, detectable in blood samples drawn 5 days postpartum, both in women depressed at that time, and in those (an overlapping, but different group) who went on to develop some features of longer term postnatal depression. It is of interest that the changes were not in V,, for 5-HT uptake or B,, for )H-imipramine binding, as had been noted in the non-puerperal illness (see Introduction). However, outside the postpartum period, there are sporadic reports in the literature of changes in affinity e.g. diurnal variation in Km for 5-HT uptake (Arora, Kregel, & Meltzer, 1984; Jerushalmy et al., 1988). A hypothesis of variable receptor affinity, based on studies of the az-adrenoreceptor, has recently been proposed (Bevan, Bevan, & Shreeve, 1989). There are also pointers in the literature to changes in receptor affinity in the immediate postpartum period. An increase in Kd for 3H-imipramine binding 5-7 days postpartum compared with other antenatal and postnatal time-points has been reported by Katona et al. (1985). In addition, the Kd of platelet ‘H-yohimbine binding has been reported to increase postnatally (Metz et al., 1983). However, it should be noted that the changes in affinity observed here are small, less than one order of magnitude, and thus may well not be of direct physiological significance. Their potential interest lies in the fact that they suggest the possibility ol generalised membrane abnormalities or abnormal circulating factors occurring in the immediate postpartum period. It would have been desirable to have obtained a second blood sample from these patients at 6 weeks postpartum but this was not practicable in the present study. It is of interest that Butler and Leonard (1986), who did examine such a group of severely depressed postpartum women, found a significant decrease in V,,,, of 5-HT uptake with no change in Km. It is possible that the changes we have observed are confined to the very early puerperium and that, later, the biochemical correlates of postnatal depression are the same as those of depression occurring at other times.
S-HT KINETICS IN POSTNATAL DYSPHORIA
13
A massive fall in circulating oestrogen and progesterone occurs at parturition. These hormones are known to act on central and peripheral monoamine centres (e.g., Ehrenkranz, 1976; Biegon, Reches, Snyder, & McEwen, 1983). It has been suggested that changes in postpartum mood are linked with this fall although, as yet, there is no direct evidence for this (Nott, Franklin, Armitage, & Gelder, 1976; Kuevi et al., 1983). In addition, there is little experimental evidence of the Km for 5-HT uptake or Kd for 3H-imipramine binding varying with such hormonal changes. Castren and Tuomisto (1983) failed to find differences in Km or V,,, for 5-HT uptake between women in late pregnancy and those during the first 9 days after delivery, despite vast differences in hormone balance. Even though no consistent changes have been found in the Km of 5-HT uptake during different phases of the menstrual cycle (Taylor, Matthew, & Weinmann, 1984; Tam, Chan, & Lee, 1985; Ashby, Carr, Cook, Steptoe, & Franks, 1988), it is of interest that a significant correlation has been noted between menstrual behavioural changes and this variable (Taylor et al., 1984). 3H-Imipramine binding does not appear to vary through the menstrual cycle (Stowell, McIntosh, Cooke, & Ellis, 1988). There are several possible technical factors that can affect the measurement of imipramine binding. In this study, we employed intact platelets rather than a membrane preparation, and this should eliminate possible variations due to different amounts of intracellular protein. However, studies using both methods have found a reduced B,,, in depressed patients compared with controls (Meltzer & Arora, 1991). We also used 10 PM desipramine to define nonspecific binding and there is now evidence that lo-100 FM desipramine displaces 3H-imipramine binding from more than one site. A single saturable high affinity 3H-imipramine binding site has been defined in platelets (Marcusson & Tiger, 1988) and brain (Arora & Meltzer, 1989), using 5-HT as displacing agent. However, there is no evidence that this site is reduced in depression. It is known that changes in Km or Kd are extremely sensitive to experimental conditions and to drug or metabolite residues in the platelets. 5-HT accumulation by the platelet is, for example, highly dependent on the presence of sodium ions; sodium-free medium abolishes uptake, whereas the addition of sodium stimulates it, causing a reduction in Km (Sneddon, 1983). The affinity of imipramine for its binding site is also dependent on a sodium ion contribution (Abbott, Briley, Langer, & Setter, 1982). In this present study, however, the sodium concentration in the incubation medium was controlled and there was no difference in plasma sodium (or any other analyte measured) between depressed and non-depressed groups. However, even though there were no obvious drug effects (in that “analgesic only” patients showed similar results to the whole group), it would seem necessary to confirm this finding in a larger group of drug-free patients. It is unlikely that drug abuse was a confounding factor in this group of women; none of the recruits were reported as abusers during their pregnancy. There have been few biochemical studies to date differentiating women with postpartum dysphoria from others. One finding, which may be relevant to the current observations, is that free plasma tryptophan is low in women depressed on the sixth day postpartum (Stein, Milton, Bebbington, Wood, & Coppen, 1976; Handley, Dunn, Baker, Cockshott, & Gould, 1977). Such depletion might lead directly to changes in processes governing 5-HT metabolism because tryptophan is a precursor of 5-HT or indirectly
74
PATRICIA HANNAH et al.
if, for example, tryptophan were the precursor of a competitive inhibitor of 5-HT uptake. The present study, then, has found evidence for a reduction in Km of 5-HT uptake in platelets sampled 5 days postpartum in women who scored L 10 on the EPDS at this time, and an increase in Kd for imipramine binding in these platelets in patients who went on to score 2 10 at 6 weeks. If confirmed, these findings suggest that the biochemistry of mood changes occurring in the immediate postpartum period is somewhat different from that occurring at other times of life. References Abbott, W., Briley, M. S., Langer, S. Z., & Setter, M. (1982). Sodium shift of the inhibition of j3Hjimipramine binding by 5-HT and 5-HT uptake blockers but not by tricyclic antidepressants. &ins/t Journal of Pharmacology, 76, 29%‘. Arora, R. C., Kregel, L., & Meltzer, H. Y. (1984). Circadian rhythm of serotonin uptake in the blood platelets of normal controls. Biological Psychiatry, 19, 1579-1584. Arora, R. C., & Meltzer, H. Y. (1989). Serotonergic measures in the brains of suicide victims: 5-HT, binding sites in the frontal cortex of suicide victims and control subjects. American Journal of Psychiatry, 146, 730-736. Ashby, C. R., Carr, L. A., Cook, C. L., Steptoe, N. M., &Franks, D. D. (1988). Alteration of platelet serotonergic mechanisms and monoamine oxidase activity in premenstrual syndrome. Biologica/ fsychiutrv, 24, 225-233. Bevan, J. A., Bevan, R. D., & Shreeve, S. M. (1989). Variable receptor affinity hypothesis. Federation ofAmerican Societies for Experimental Biology Journul, 3, 1696- 1704. Biegon, A., Reches, A., Snyder, S. L., & McEwen, B. S. (1983). Serotonergic and noradrenergic receptors in the rat bain: modulation by chronic exposure to ovarian hormones. Life Sciences, 32, 2015-2021. Briley, M. S., Langer, S. Z., Raisman, R., Sechter, D., & Zarifian, E. (1980). 3H-Imipramine binding sites are decreased in platelets of untreated depressed patients. Science, 209, 303-305. Brockington, I. (1982). Puerperal psychosis. In: Brockington, 1. F. and Kumar, R. (Eds), Motherhood and mental illness. (pp. 37-70). London: Academic Press. Butler, J., & Leonard, B. E. (1986). Postpartum depression and the effect of nomifensine treatment. Inrernai/onu/ Clinical Psychopharmacology, 1, 244-252. Castren, E., & Tuomisto, J. (1983). Influence of the hormonal balance of late pregnancy on the active uptake of 5-hydroxytryptamine by human blood platelets. Medical Biology, 61, 168-171. Cox, J. L., Holden, J. M., & Sagovsky, R. (1987). Detection of postnatal depression: development of the IO-item Edinburgh Postnatal Depression Scale. British Journal of Psychiatry, 150, 782-786. Cooper, P. J., Campbell, E. A., Day, A., Kennerley, H., &Bond, A. (1988). Non-psychotic psychiatric disorder after childbirth: a prospective study of prevalence, incidence, course and nature. British Journu/ of Psychiatry, 152, 799-806. Coppen, A. L., Swade, C., &Wood, K. (1978). Platelet 5.hydroxytryptamine accumulation in depressive illness. Clintcu Chimicu Aclu, 87, 165-168. Ehrenkrana, J. R. L. (1976). Effects of sex steroids on serotonin uptake in blood platelets. Actu Endocrinologicu, 83, 420-428. Geaney, D. P., Rutterford, M. G., Elliott, J. M., Schachtcr, M., Peer, K. M. S., & Grahame-Smith, D. G. (1984). Decreased platelet (‘H)-imipramine binding sites in classical migraine. Journul ofNeurology, ,Veurosurgery, and Psychiatry, 47, 720-723. George, A., & Sandler, M. (1988). Endocrine and biochemical studies in puerperal mental disorders. In: I. F. Brockington and R. Kumar (Eds) Motherhood and Mental l//ness 2. (pp. 78-l 12). London: Academic Press. Handley, S. L., Dunn, T. L., Baker, J. M., Cockshott, C., & Gould, S. (1977). Mood changes in the puerperium and plasma tryptophan and cortisol. British Medical Journal, 2, 18-22. Hapgood, C. C., Elkind, G. S., & Wright, J. J. (1988). Maternity blues: phenomena and relationship to later postpartum depression. Australian and New Zealand Journal of Psychiarry, 22, 299-306. Healy, D., & Leonard, B. E. (1987). Monoamine transport in depression: kinetics and dynamics. Journal of Affective Disorders, 12. 91- 103 Jerushalmy, Z., Modai, I., Chachkes, O., Mark, M., Valewski, A., Chachkes, M., & Tyano, S. (1988). Kinetic values of active serotonin transport by platelets of bipolar, unipolar and schirophrcnic patients at 2 and 8am. Neuropsychobio/og_v, 20, 57-61.
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Kanof, P. D., Coccaro, E. F., Johns, C. A., Siever, L. J., & Davies, K. L. (1987). Platelet (3H-imipramine) binding in psychiatric disorders. Biological Psychiatry, 22, 278-286. Katona, C. L. E., Theodorou, A. E., Missouris, C. G., Bourke, M. P., Horton, R. W., Moncrieff, D., Paykel, E. S., & Kelly, J. S. (1985). Platelet 3H-imipramine binding in pregnancy and the puerperium. Psychiatry Research, 14, 33-37. Kennerley, H., & Gath, D. (1986). Maternity blues reassessed. Psychiatry Develoment, 1, 1-17. Kuevi, V., Carson, R., Dixon, A. F., Everard, D. M., Hall, J. M., Hole, D., Whitehead, S. A., Wilson, C. A., & Wise, J. C. (1983). Plasma amine and hormone changes in post-partum blues. ClinicalEndocrinology, 19, 39-46. Kumar, R. (1982). Neurotic disorders in childbearing women. In Brockington, I. F. & Kumar, R. (Eds) Motherhood and mental illness (pp. 71-l 18). London: Academic Press. Kumar, R., & Robson, K. M. (1984). A prospective study of emotional disorders in childbearing women. British Journal of Psychiatry, 144, 35-47. Lowry, 0. H., Rosebrough, N. J., Farr, A. L., & Randall, R. J. (1951). Protein measurement with the Folin phenol reagent. Journal of Biological Chemistry, 193, 265-275. Marcusson, J. O., & Tiger, G. (1988). [3H]lmipramine binding of protein nature in human platelets: Inhibition by 5-hydroxytryptamine and 5-hydroxytryptamine uptake inhibitors. Journal of Neurochemistry, 50, 1032-1036. Metz, A., Cowen, P. J., Gelder, M. G., Stump, K., Elliott, J. M., & Grahame-Smith, D. G. (1983). Changes in platelet ol-adrenoceptor binding post-partum: possible relation to maternity blues. Lancer, i, 495-498. Meltzer, H. Y., & Arora, R. C. (1991). Platelet serotonin studies in affective disorders: evidence for a serotonergic abnormality? In: Sandler, M., Coppen, A. and Harnett, S. (Eds), S-Hydroxytryptamine inpsychiatry-aspectrum of ideas (pp. 50-89). Oxford: Oxford University Press. Nott, P. N., Franklin, M., Armitage, C., & Gelder, M. G. (1976). Hormonal changes in post-partum blues. Clinical Endocrinology, 19, 39-46. O’Hara, M. W. (1987). Post-partum ‘blues’, depression, and psychosis: a review. Journal of Psychosomatic Obstetrics & Gynecology, 7, 205-227. O’Hara, M. W., & Zekoski, E. M. (1988). Postpartum depression: A comprehensive review. In I. F. Brockington, R. Kumar (Eds), Motherhood and mental illness 2 (pp. 17-63). London: Academic Press. Paul, S. M., Rehavi, M., Skolnick, P., Ballenger, J. C., &Goodwin, F. K. (1981). Depressed patients have decreased binding of tritiated imipramine to platelet serotonin transporter. Archives of General Psychiatry, 38, 1315-1317. Reich, T., & Winokur, G. (1970). Postpartum psychoses in patients with manic depressive disease. Journal of Nervous and Mental Disorders, 151, 66-68. Reveley, M. A., Glover, V., Sandler, M., & Coppen, A. (1981). Increased platelet monoamine oxidase activity in affective disorders. Psychopharmacology, 13, 257-260. Snalling, D., Asberg, M., Edman, G., & Oreland, L. (1987). Markers for vulnerability to psychopathology: Temperament traits associated with platelet MAO activity. Acta Psychiatrica Scandinavica, 76, 172-182. Sneddon, J. M. (1983). Blood platelets as a model for monoamine-containing neurones. Progress in Neurobiology, 1, 151-198. Stein, G. (1982). The maternity blues. In Brockington, I. F., and Kumar, F. (Eds). Motherhood and mental illness (pp. 119-154). London: Academic Press. Stein, G. S., Milton, F., Bebbington, P., Wood, K., & Coppen, A. (1976). Relationship between mood disturbances and free and total plasma tryptophan in post-partum women. British Medical Journal, 2, 457-459. Stowell, L. I., McIntosh, C. J., Cooke, R., &Ellis, P. M. (1988). Adrenoceptor and imipramine receptor binding during the menstrual cycle. Acta Psychiatrica Scandinavica, 78, 366-368. Suranyi-Cadotte, H. E., Quirion, R., Nair, N. P. V., Lafaille, F., & Schwarz, G. (1985). lmipramine treatment differentially affects platelet ‘H-imipramine binding and serotonin uptake in depressed patients. Life Sciences, 36, 795-799. Tam, W. Y. K., Chan, M-Y., & Lee, P. H. K. (1985). The menstrual cycle and platelet 5.HT uptake. Psychosomatic Medicine, 47, 352-362. Taylor, 0. L., Matthew, R. J., & Weinman, M. L. (1984). Serotonin levels and platelet uptake during premenstrual tension. Neuropsychobiology, 12, 16-18. Tuomisto, J., & Tukiainen, E. (1976). Decreased uptake of S-hydroxytryptamine in blood platelets from depressed patients. Nature, 262, 596-598.
