29
Psychiatry Research, 32~29-34 Elsevier
lmipramine Binding Psychogenic Pain
in Depressed
Patients
With
Erling T. Mellerup, Henrik Dam, Myung Y. Kim, Dorte Loldrup, Per Plenge, Raben Rosenberg, and Susan Schepelern Received July 7. 1989; accepted December
12, 1989.
Abstract. lmipramine binding to platelet membranes from depressed patients was analyzed. The patients were divided into two groups: one with depression alone, another with depression and psychogenic pain. The depressed patients with psychogenic pain had lower imipramine binding than the depressed patients without pain. Key Words. JH-imipramine chogenic pain.
binding,
human
blood
platelets,
depression,
psy-
A specific high-affinity binding site for imipramine, chlorimipramine, and other serotonin uptake inhibitors is located on the serotonin transport mechanism in membranes from serotonergic neurons and from platelets (Briley et al., 1979; Raisman et al., 1979; Langer et al., 1980; Fuxe et al., 1983). Because any function or structure related to the serotonergic system may be of potential importance in mental illness, imipramine binding in platelets from psychiatric patients has been widely studied. Most studies have been with depressed patients, and a majority of these studies have found that depressed patients have a lower number of platelet imipramine binding sites compared with healthy controls. However, about one third of the studies have not found such a difference between patients and controls (Mellerup and Plenge, 19886). This discrepancy could stem from methodological problems as it has been found that treatment with chlorimipramine strongly reduces platelet imipramine binding (Poirier et al., 1984; Mellerup and Plenge, 1986). Because it is practically impossible to remove chlorimipramine from the platelet membranes by the usual washing procedures (Mellerup and Plenge, 1988a), it is possible that some low binding values in depressed patients were due to contamination with chlorimipramine. However, many patients with low imipramine binding have not received this antidepressant, indicating that additional explanations for the variation among various studies should be considered. A possibility is that low platelet imipramine binding is
Erling T. Mellerup, Ph.D., Myung Y. Kim, M.D., Per Plenge, Ph.D., and Raben Rosenberg, M.D., are at the Psychochemistry Institute and Psychiatric Department, Rigshospitalet, Copenhagen, Denmark. Henrik Dam, M.D., is at Copenhagen Municipal Hospital. Dorte Loldrup, M.D., is at Frederiksberg County Hospital. Susan Schepelern, M.D., is at Frederiksberg Hospital. Dr. Kim is presently in the Department of Psychiatry, Medical College, Pusan National University, Pusan, Republic of Korea. (Reprint requests to Dr. E.T. Mellerup, Psychochemistry Institute, Rigshospitalet, 9 Blegdamsvej, DK2100 Copenhagen 0, Denmark.) 0165-1781/90/$03.50
@ 1990 Elsevier Scientific
Publishers Ireland
Ltd
30
characteristic only for one or more subgroups of depressed patients. If such subgroups were absent or present to varying degrees in local populations of depressed patients due to diagnostic, ethnic, or cultural factors, it would explain why differences between depressed patients and control persons were found in some studies but not in others. The aim of the present study was to analyze a subgroup of depressed patients who, in addition to their affective symptoms, also suffered from psychogenic pain. The selection of this particular group was prompted by three previous studies of patients with chronic psychogenic pain. Magni et al. (1987) studied 16 patients suffering from chronic pain without organic pathology. The patients did not take antidepressants. Platelet imipramine binding was lower in the patients than in the controls, primarily due to very low binding in half of the patients. In another study 215 patients with chronic psychogenic pain were divided into two groups, one with affective symptoms in addition to pain and one with pain alone (Mellerup et al., 1988). The former group had lower imipramine binding than the patients with pain alone and also had lower binding than the controls. In a third study of 43 patients with idiopathic pain syndrome who also showed affective symptoms, lower platelet imipramine binding was found in the patients compared with the control subjects (Eberhard et al., 1989).
Methods Patients. Forty depressed inpatients were initially included in the study. The patients fulfilled the Research Diagnostic Criteria for depressive disorder (Spitzer et al., 1978). Severity of depression was measured with the Hamilton Rating Scale for Depression (Hamilton, 1960); levels of anxiety were assessed by Hamilton Rating Scale for Anxiety (Hamilton, 1959). The degree of psychogenic pain was estimated through a visual analog scale divided into five parts: 0, no sensation at all or some sensation but not unpleasant or uncomfortable; I, sensation unpleasant or uncomfortable but not painful; 2, mildly painful; 3, moderately painful; and 4, severely painful. The exclusion criteria were physical disease that could cause pain, alcohol or drug dependence, treatment with chlorimipramine, and age below 18 years. Almost all the patients were in treatment with antidepressants or electroconvulsive therapy. After the binding analysis was performed, those patients who had K, > I nM were excluded due to the possibility that a high Kd value was caused by drug residues in the platelet membrane. Blood Sampling and Isolation of Platelets. In the morning, blood (- 20 ml) was collected into plastic tubes containing anticoagulant (0.25 ml 0. I5 h4 EDTA/ IO ml blood). After gentle mixing, centrifugation at 20013 for 20 min at room temperature, the platelet-rich plasma was collected and centrifuged at 10,OOOgfor IO min at 4 “C. The supernatant was discarded. The drained platelet pellet was stored at -80 ‘C until analysis or transportation in dry ice. Preparation
of Platelet Membranes. The isolated platelets were washed twice with 8 ml buffer (I 50 mM NaCI, 20 mM EDTA, 50 mM Tris HCl,pH 7.5). The platelets were lysed and homogenized in 8 ml buffer (5 mM EDTA, 5 mM Tris HCI, pH 7.5) using an Ultra-thurrax homogenizer for 5 set at about two third of full speed. The membranes were precipitated and washed twice with 8 ml buffer (120 mM NaCI, 5 mM EDTA, 50 mM Tris HCI, pH 7.5) 30,00013 for IO min at 4 “C. The membranes were resuspended in 4 ml of the latter buffer. Protein concentration in this final suspension was determined by a modification of the Lowry method (Peterson, 1977). Binding Assay. The platelet
membrane
suspension
(lOO/.d) was incubated
with 450~1 buffer
31 (120 mM NaCI,
5 mM EDTA, 50 mM Tris HCI, pH 7.5) and 50 ~1 JH-imipramine (20 Ci/ mmol, Amersham, England), final concentration of isotope: 0.2, 0.5, 0.7, I .O, I .5, and 2.0 nh4. The incubation lasted for 3 hours at 0 “C and was terminated by the addition of 5 ml ice-cold incubation buffer and rapid filtration through Whatman GF/ F glass-fiber filters, which were soaked with 0.5% polyethylenimine. The filters were washed 4 times with 5 ml ice-cold buffer, dried at room temperature, and counted in 3 ml Picofluor I5 in a scintillation counter. Nonspecific binding was determined in the presence of I /.1h4 desmethylimipramine. Specific binding was calculated from the difference between total binding and nonspecific binding.
Calculations imipramine Differences
and Statistics. The number of binding sites, B,,,, and the affinity between the and the binding site, expressed as Kdr were calculated from Scatchard plots. between mean values were compared by the nonparametric Mann-Whitney test.
Results After exclusion of patients with high K,, values, 33 remained. These patients were divided into two groups-one showing little or no pain and another group showing moderate to severe pain. Table I shows the results for these two groups. No significant differences were found with respect to age, degree of depression or anxiety, or Kd. However, the number of platelet imipramine binding sites was significantly smaller in the group with depression and pain compared with the depressed group without pain. Table 1 also reveals that the eight patients with moderate to severe pain were women; for this reason, the results were recalculated with the omission of the male patients.
Table 1. lmipramine binding to platelet membranes from depressed patients with psychogenic pain ( frfo%g protein)
(Z)
Hamilton depression score
Hamilton anxiety score
Depression alone (17 females, 8 males; mean age 57)
Mean SD
1270
0.6
21
16
240
0.3
8
6
1050
0.7
20
19
200
0.3
4
7
Depression with pain (8 females; mean age 64)
Mean SD
p < 0.03
Table 2 shows the results for the depressed women. Again, the only significant difference was the difference in the number of binding sites between the depressed women with pain and the depressed women without pain. Although no significant difference was found with respect to age, Tables 1 and 2 show that the group of depressed patients with pain was older than the other group. To examine a possible influence of age on the B,,,,, results, a correlation analysis was performed and demonstrated that age did not correlate significantly with B,,, (r = -0.28, p < 0.12).
32
Table 2. lmipramine binding to platelet membranes from depressed women with psychogenic pain (frfGng protein)
(2)
Hamilton depression score
Hamilton anxiety score
Depression alone (17 females; mean age 56)
Mean SD
1320
0.7
20
16
250
0.3
8
6
1050
0.7
20
19
200
0.3
4
7
Depression with pain (8 females; mean age 64)
Mean SD
p < 0.02
Although high Kd values had been excluded, it was further investigated whether B,,,,, values were influenced by antidepressants. The patients were divided into two groups: one which, at the time of blood sampling, was not receiving any antidepressants at all, and another which was receiving antidepressants. The B,,,,, for the former group was 1216 I!I 210 fmol/mg protein as compared to 1215 + 260 fmol/ mg protein for the latter group. Despite the psychogenic nature of the pain in the eight patients with moderate to severe pain, four of them took salycylates or acetaminophen. In addition, 1 of the 25 patients without pain took salycylates. When the four pain patients who took an analgesic agent were compared with the four who did not use analgesics, it was found that B,,,,, was 1190 + 80 fmol/mg protein for the former group versus 915 f 170 fmol/ mg protein for the latter 0, < 0.03).
Discussion In a previous study, the imipramine binding in platelets from patients with chronic psychogenic pain was analyzed (Mellerup et al., 1988). These patients were subdivided according to the absence or presence of symptoms of depression or anxiety. The group of pain patients with coexisting depression or anxiety had a significantly lower level of platelet imipramine binding than pain patients without affective symptoms. In the present study, the patients were primarily depressed and they were then subdivided according to the absence or presence of pain symptoms without somatic origin. The group of depressed patients who also suffered from psychogenic pain had a significantly lower level of platelet imipramine binding compared with the depressed patients without pain. The difference was not caused by sex distribution, age, or antidepressant medication. The finding of lower B,,, values in those pain patients who did not take analgesics compared with those who did, is difficult to evaluate because the number of patients in each group was as low as four. However, in an ongoing study of imipramine binding in patients in a pain clinic, the question of a possible effect of analgesics can be addressed. In two earlier studies we were unable to demonstrate a decrease in platelet
33
imipramine binding in depressed patients compared with controls (Mellerup et al., 1982; Plenge et al., 1988). Now we have found decreased imipramine binding in a selected group of depressed patients (i.e., those with psychogenic pain symptoms in addition to their affective symptoms). As this group is relatively small (8 of 33 in this study), these patients would not have been able to produce a significantly lower level of imipramine binding in the total group of depressed patients compared with controls. However, if patients with chronic psychogenic pain and affective symptoms had been included in the depressed population, instead of being patients at various somatic departments, our previous studies might also have shown decreased imipramine binding in depressed patients. From a clinical point of view, it is interesting to speculate whether patients with low imipramine binding in other studies also might have included some with psychogenic pain symptoms. From a more theoretical point of view, it would be interesting to know whether the role of serotonin in pain perception as well as in the etiology binding
of depression may in any way be related to the finding in patients with both pain and affective symptoms.
of low imipramine
Acknowledgment. This study was supported in part by the Danish Medical Council and the Lundbeck Fonden of 1984. We thank Bente Bennike for excellent assistance.
Research technical
References Briley, M.S.; Raisman, R.; and Langer, S.Z. Human platelets possess high-affinity binding sites for 3H-imipramine. European Journaf of fharmacology, 58:347-348, 1979. Eberhard, G.; von Knorring, L.; Mellerup, E.T.; Nielsson, H.L.; Plenge, P.; and Sundequist, U. 3H-imipramine binding in idiopathic pain syndromes. fain, 38:261-267, 1989. Fuxe, K.; Calza, L.; Benfenati, F.; Zini, I.; and Agnati, L. Quantitative autoradiographic localization of 3H-imipramine binding sites in the brain of the rat: Relationship to ascending S-hydroxytryptamine neuron systems. Proceedings of the National Academy of Sciences of the United States of America 80:3836-3840, 1983. Hamilton, M. The assessment of anxiety states by rating. British Journal of Medicine & Psychology, 3250-55, 1959. Hamilton, M. A rating scale for depression. Journal of Neurology. Neurosurgery, and Psychiatry, 23:56-62, 1960. Magni, G.; Andreoli, F.; Arduino, C.; Arsie, D.; Ceccherelli, G.; Ambrosio, F.; and Eandi, M. 3H-imipramine binding sites are decreased in platelets of chronic pain patients. Acta Psychiatric4 Scandinavica, 75: IO8 (I 987). Mellerup, E.T.; Beth, P.; Hansen, H.J.; Langemark, M.; Loldrup, D.; and Plenge, P. Platelet 3H-imipramine binding in psychogenic pain disorders. Psychiatry Research, 26: l49156, 1988. Mellerup, E.T., and Plenge, P. Chlorimipramine-but not imipramine-rapidly reduces 3H-imipramine binding in human platelet membranes. European Journal of Pharmacology, 126:155-158, 1986. Mellerup, E.T., and Plenge, P. High non-specific binding of chlorimipramine to platelet and neuronal membranes. Psychopharmacology, (Suppl. 96):298, 19884. Mellerup, E.T., and Plenge, P. lmipramine binding in depression and other psychiatric conditions. Acta Psychiatric4 Scandinavica, 78 (Suppl. 345):61-68, 19886. Mellerup, E.T.; Plenge, P.; and Rosenberg, R. 3H-imipramine binding sites in platelets from psychiatric patients. Psychiatry Research, 7:221-227, 1982.
34 Peterson, G.L. A simplification of the protein assay method of Lowry et al. which is more generally applicable. Analytical Biochemistry. 83:346-356, 1977. Plenge, P.; Mellerup, E.T.; and Gjerris, A.G. lmipramine binding in depressive patients, diagnosed according to different criteria. Acta Psychiatrica Scandinavica. 78: I56- 158, 1988. Poirier, M.F.; Loo, H.; Sechter, D.; Zarafian, E.; Galzin, A.M.; Schoemaker, H.; Segonzac, A.; and Langer, S.Z. 3H-imipramine binding and 3H-5HT uptake in human blood platelets: Changes after one week of chlorimipramine treatment. European Journal qf Pharmacology, IO6:629-633,
1984.
Raisman, R.; Briley, M.; and Langer, S.Z. Specific tricyclic antidepressant binding sites in rat brain. Nature, 28 I: 148-150, 1979. Spitzer, R.L.; Endicott, J.; and Robins, E. Research Diagnostic Criteria: Rationale and reliability. Archives ofGenera Psychiatry. 35:773-782, 1978.
Psychiatry Research, 32~29-34 Elsevier
lmipramine Binding Psychogenic Pain
in Depressed
Patients
With
Erling T. Mellerup, Henrik Dam, Myung Y. Kim, Dorte Loldrup, Per Plenge, Raben Rosenberg, and Susan Schepelern Received July 7. 1989; accepted December
12, 1989.
Abstract. lmipramine binding to platelet membranes from depressed patients was analyzed. The patients were divided into two groups: one with depression alone, another with depression and psychogenic pain. The depressed patients with psychogenic pain had lower imipramine binding than the depressed patients without pain. Key Words. JH-imipramine chogenic pain.
binding,
human
blood
platelets,
depression,
psy-
A specific high-affinity binding site for imipramine, chlorimipramine, and other serotonin uptake inhibitors is located on the serotonin transport mechanism in membranes from serotonergic neurons and from platelets (Briley et al., 1979; Raisman et al., 1979; Langer et al., 1980; Fuxe et al., 1983). Because any function or structure related to the serotonergic system may be of potential importance in mental illness, imipramine binding in platelets from psychiatric patients has been widely studied. Most studies have been with depressed patients, and a majority of these studies have found that depressed patients have a lower number of platelet imipramine binding sites compared with healthy controls. However, about one third of the studies have not found such a difference between patients and controls (Mellerup and Plenge, 19886). This discrepancy could stem from methodological problems as it has been found that treatment with chlorimipramine strongly reduces platelet imipramine binding (Poirier et al., 1984; Mellerup and Plenge, 1986). Because it is practically impossible to remove chlorimipramine from the platelet membranes by the usual washing procedures (Mellerup and Plenge, 1988a), it is possible that some low binding values in depressed patients were due to contamination with chlorimipramine. However, many patients with low imipramine binding have not received this antidepressant, indicating that additional explanations for the variation among various studies should be considered. A possibility is that low platelet imipramine binding is
Erling T. Mellerup, Ph.D., Myung Y. Kim, M.D., Per Plenge, Ph.D., and Raben Rosenberg, M.D., are at the Psychochemistry Institute and Psychiatric Department, Rigshospitalet, Copenhagen, Denmark. Henrik Dam, M.D., is at Copenhagen Municipal Hospital. Dorte Loldrup, M.D., is at Frederiksberg County Hospital. Susan Schepelern, M.D., is at Frederiksberg Hospital. Dr. Kim is presently in the Department of Psychiatry, Medical College, Pusan National University, Pusan, Republic of Korea. (Reprint requests to Dr. E.T. Mellerup, Psychochemistry Institute, Rigshospitalet, 9 Blegdamsvej, DK2100 Copenhagen 0, Denmark.) 0165-1781/90/$03.50
@ 1990 Elsevier Scientific
Publishers Ireland
Ltd
30
characteristic only for one or more subgroups of depressed patients. If such subgroups were absent or present to varying degrees in local populations of depressed patients due to diagnostic, ethnic, or cultural factors, it would explain why differences between depressed patients and control persons were found in some studies but not in others. The aim of the present study was to analyze a subgroup of depressed patients who, in addition to their affective symptoms, also suffered from psychogenic pain. The selection of this particular group was prompted by three previous studies of patients with chronic psychogenic pain. Magni et al. (1987) studied 16 patients suffering from chronic pain without organic pathology. The patients did not take antidepressants. Platelet imipramine binding was lower in the patients than in the controls, primarily due to very low binding in half of the patients. In another study 215 patients with chronic psychogenic pain were divided into two groups, one with affective symptoms in addition to pain and one with pain alone (Mellerup et al., 1988). The former group had lower imipramine binding than the patients with pain alone and also had lower binding than the controls. In a third study of 43 patients with idiopathic pain syndrome who also showed affective symptoms, lower platelet imipramine binding was found in the patients compared with the control subjects (Eberhard et al., 1989).
Methods Patients. Forty depressed inpatients were initially included in the study. The patients fulfilled the Research Diagnostic Criteria for depressive disorder (Spitzer et al., 1978). Severity of depression was measured with the Hamilton Rating Scale for Depression (Hamilton, 1960); levels of anxiety were assessed by Hamilton Rating Scale for Anxiety (Hamilton, 1959). The degree of psychogenic pain was estimated through a visual analog scale divided into five parts: 0, no sensation at all or some sensation but not unpleasant or uncomfortable; I, sensation unpleasant or uncomfortable but not painful; 2, mildly painful; 3, moderately painful; and 4, severely painful. The exclusion criteria were physical disease that could cause pain, alcohol or drug dependence, treatment with chlorimipramine, and age below 18 years. Almost all the patients were in treatment with antidepressants or electroconvulsive therapy. After the binding analysis was performed, those patients who had K, > I nM were excluded due to the possibility that a high Kd value was caused by drug residues in the platelet membrane. Blood Sampling and Isolation of Platelets. In the morning, blood (- 20 ml) was collected into plastic tubes containing anticoagulant (0.25 ml 0. I5 h4 EDTA/ IO ml blood). After gentle mixing, centrifugation at 20013 for 20 min at room temperature, the platelet-rich plasma was collected and centrifuged at 10,OOOgfor IO min at 4 “C. The supernatant was discarded. The drained platelet pellet was stored at -80 ‘C until analysis or transportation in dry ice. Preparation
of Platelet Membranes. The isolated platelets were washed twice with 8 ml buffer (I 50 mM NaCI, 20 mM EDTA, 50 mM Tris HCl,pH 7.5). The platelets were lysed and homogenized in 8 ml buffer (5 mM EDTA, 5 mM Tris HCI, pH 7.5) using an Ultra-thurrax homogenizer for 5 set at about two third of full speed. The membranes were precipitated and washed twice with 8 ml buffer (120 mM NaCI, 5 mM EDTA, 50 mM Tris HCI, pH 7.5) 30,00013 for IO min at 4 “C. The membranes were resuspended in 4 ml of the latter buffer. Protein concentration in this final suspension was determined by a modification of the Lowry method (Peterson, 1977). Binding Assay. The platelet
membrane
suspension
(lOO/.d) was incubated
with 450~1 buffer
31 (120 mM NaCI,
5 mM EDTA, 50 mM Tris HCI, pH 7.5) and 50 ~1 JH-imipramine (20 Ci/ mmol, Amersham, England), final concentration of isotope: 0.2, 0.5, 0.7, I .O, I .5, and 2.0 nh4. The incubation lasted for 3 hours at 0 “C and was terminated by the addition of 5 ml ice-cold incubation buffer and rapid filtration through Whatman GF/ F glass-fiber filters, which were soaked with 0.5% polyethylenimine. The filters were washed 4 times with 5 ml ice-cold buffer, dried at room temperature, and counted in 3 ml Picofluor I5 in a scintillation counter. Nonspecific binding was determined in the presence of I /.1h4 desmethylimipramine. Specific binding was calculated from the difference between total binding and nonspecific binding.
Calculations imipramine Differences
and Statistics. The number of binding sites, B,,,, and the affinity between the and the binding site, expressed as Kdr were calculated from Scatchard plots. between mean values were compared by the nonparametric Mann-Whitney test.
Results After exclusion of patients with high K,, values, 33 remained. These patients were divided into two groups-one showing little or no pain and another group showing moderate to severe pain. Table I shows the results for these two groups. No significant differences were found with respect to age, degree of depression or anxiety, or Kd. However, the number of platelet imipramine binding sites was significantly smaller in the group with depression and pain compared with the depressed group without pain. Table 1 also reveals that the eight patients with moderate to severe pain were women; for this reason, the results were recalculated with the omission of the male patients.
Table 1. lmipramine binding to platelet membranes from depressed patients with psychogenic pain ( frfo%g protein)
(Z)
Hamilton depression score
Hamilton anxiety score
Depression alone (17 females, 8 males; mean age 57)
Mean SD
1270
0.6
21
16
240
0.3
8
6
1050
0.7
20
19
200
0.3
4
7
Depression with pain (8 females; mean age 64)
Mean SD
p < 0.03
Table 2 shows the results for the depressed women. Again, the only significant difference was the difference in the number of binding sites between the depressed women with pain and the depressed women without pain. Although no significant difference was found with respect to age, Tables 1 and 2 show that the group of depressed patients with pain was older than the other group. To examine a possible influence of age on the B,,,,, results, a correlation analysis was performed and demonstrated that age did not correlate significantly with B,,, (r = -0.28, p < 0.12).
32
Table 2. lmipramine binding to platelet membranes from depressed women with psychogenic pain (frfGng protein)
(2)
Hamilton depression score
Hamilton anxiety score
Depression alone (17 females; mean age 56)
Mean SD
1320
0.7
20
16
250
0.3
8
6
1050
0.7
20
19
200
0.3
4
7
Depression with pain (8 females; mean age 64)
Mean SD
p < 0.02
Although high Kd values had been excluded, it was further investigated whether B,,,,, values were influenced by antidepressants. The patients were divided into two groups: one which, at the time of blood sampling, was not receiving any antidepressants at all, and another which was receiving antidepressants. The B,,,,, for the former group was 1216 I!I 210 fmol/mg protein as compared to 1215 + 260 fmol/ mg protein for the latter group. Despite the psychogenic nature of the pain in the eight patients with moderate to severe pain, four of them took salycylates or acetaminophen. In addition, 1 of the 25 patients without pain took salycylates. When the four pain patients who took an analgesic agent were compared with the four who did not use analgesics, it was found that B,,,,, was 1190 + 80 fmol/mg protein for the former group versus 915 f 170 fmol/ mg protein for the latter 0, < 0.03).
Discussion In a previous study, the imipramine binding in platelets from patients with chronic psychogenic pain was analyzed (Mellerup et al., 1988). These patients were subdivided according to the absence or presence of symptoms of depression or anxiety. The group of pain patients with coexisting depression or anxiety had a significantly lower level of platelet imipramine binding than pain patients without affective symptoms. In the present study, the patients were primarily depressed and they were then subdivided according to the absence or presence of pain symptoms without somatic origin. The group of depressed patients who also suffered from psychogenic pain had a significantly lower level of platelet imipramine binding compared with the depressed patients without pain. The difference was not caused by sex distribution, age, or antidepressant medication. The finding of lower B,,, values in those pain patients who did not take analgesics compared with those who did, is difficult to evaluate because the number of patients in each group was as low as four. However, in an ongoing study of imipramine binding in patients in a pain clinic, the question of a possible effect of analgesics can be addressed. In two earlier studies we were unable to demonstrate a decrease in platelet
33
imipramine binding in depressed patients compared with controls (Mellerup et al., 1982; Plenge et al., 1988). Now we have found decreased imipramine binding in a selected group of depressed patients (i.e., those with psychogenic pain symptoms in addition to their affective symptoms). As this group is relatively small (8 of 33 in this study), these patients would not have been able to produce a significantly lower level of imipramine binding in the total group of depressed patients compared with controls. However, if patients with chronic psychogenic pain and affective symptoms had been included in the depressed population, instead of being patients at various somatic departments, our previous studies might also have shown decreased imipramine binding in depressed patients. From a clinical point of view, it is interesting to speculate whether patients with low imipramine binding in other studies also might have included some with psychogenic pain symptoms. From a more theoretical point of view, it would be interesting to know whether the role of serotonin in pain perception as well as in the etiology binding
of depression may in any way be related to the finding in patients with both pain and affective symptoms.
of low imipramine
Acknowledgment. This study was supported in part by the Danish Medical Council and the Lundbeck Fonden of 1984. We thank Bente Bennike for excellent assistance.
Research technical
References Briley, M.S.; Raisman, R.; and Langer, S.Z. Human platelets possess high-affinity binding sites for 3H-imipramine. European Journaf of fharmacology, 58:347-348, 1979. Eberhard, G.; von Knorring, L.; Mellerup, E.T.; Nielsson, H.L.; Plenge, P.; and Sundequist, U. 3H-imipramine binding in idiopathic pain syndromes. fain, 38:261-267, 1989. Fuxe, K.; Calza, L.; Benfenati, F.; Zini, I.; and Agnati, L. Quantitative autoradiographic localization of 3H-imipramine binding sites in the brain of the rat: Relationship to ascending S-hydroxytryptamine neuron systems. Proceedings of the National Academy of Sciences of the United States of America 80:3836-3840, 1983. Hamilton, M. The assessment of anxiety states by rating. British Journal of Medicine & Psychology, 3250-55, 1959. Hamilton, M. A rating scale for depression. Journal of Neurology. Neurosurgery, and Psychiatry, 23:56-62, 1960. Magni, G.; Andreoli, F.; Arduino, C.; Arsie, D.; Ceccherelli, G.; Ambrosio, F.; and Eandi, M. 3H-imipramine binding sites are decreased in platelets of chronic pain patients. Acta Psychiatric4 Scandinavica, 75: IO8 (I 987). Mellerup, E.T.; Beth, P.; Hansen, H.J.; Langemark, M.; Loldrup, D.; and Plenge, P. Platelet 3H-imipramine binding in psychogenic pain disorders. Psychiatry Research, 26: l49156, 1988. Mellerup, E.T., and Plenge, P. Chlorimipramine-but not imipramine-rapidly reduces 3H-imipramine binding in human platelet membranes. European Journal of Pharmacology, 126:155-158, 1986. Mellerup, E.T., and Plenge, P. High non-specific binding of chlorimipramine to platelet and neuronal membranes. Psychopharmacology, (Suppl. 96):298, 19884. Mellerup, E.T., and Plenge, P. lmipramine binding in depression and other psychiatric conditions. Acta Psychiatric4 Scandinavica, 78 (Suppl. 345):61-68, 19886. Mellerup, E.T.; Plenge, P.; and Rosenberg, R. 3H-imipramine binding sites in platelets from psychiatric patients. Psychiatry Research, 7:221-227, 1982.
34 Peterson, G.L. A simplification of the protein assay method of Lowry et al. which is more generally applicable. Analytical Biochemistry. 83:346-356, 1977. Plenge, P.; Mellerup, E.T.; and Gjerris, A.G. lmipramine binding in depressive patients, diagnosed according to different criteria. Acta Psychiatrica Scandinavica. 78: I56- 158, 1988. Poirier, M.F.; Loo, H.; Sechter, D.; Zarafian, E.; Galzin, A.M.; Schoemaker, H.; Segonzac, A.; and Langer, S.Z. 3H-imipramine binding and 3H-5HT uptake in human blood platelets: Changes after one week of chlorimipramine treatment. European Journal qf Pharmacology, IO6:629-633,
1984.
Raisman, R.; Briley, M.; and Langer, S.Z. Specific tricyclic antidepressant binding sites in rat brain. Nature, 28 I: 148-150, 1979. Spitzer, R.L.; Endicott, J.; and Robins, E. Research Diagnostic Criteria: Rationale and reliability. Archives ofGenera Psychiatry. 35:773-782, 1978.
