Psycho pharmacology

Psychopharmacology49, 197- 200 (1976)

9 by Springer-Verlag1976

Effect of Thyrotropin-Releasing Hormone (TRH) and Antidepressant Agents on Brain Stem and Hypothalamic Multiple Unit Activity in the Cat L. KORfi~NYI*, V. TAMASY, K. LISSAK, Institute of Physiology,UniversityMedical School, 7643 P6cs, Hungary, I. K I R A L Y , J. BORSY Research Institute for PharmaceuticalChemistry,Budapest, Hungary

The EEG and M U A (multiple unit activity) of mesencephalic reticular formation (MRF), area hypothalami posterior (PH), and area hypothalami anterior (AH) were studied in chronically implanted freely moving cats. The effects ofthyrotropin-releasing hormone (TRH) and some antidepressant agents were tested on neuronal activity. Desipramine and imipramine resulted in a dose-dependent decline of M U A of all structures with the most significant decrease of activity in PH. A single injection of T R H resulted in slight or moderate gross behavioral changes and vegetative excitation lasting for 3 0 - 5 0 min with variable M U A levels. In the course of repetitive T R H treatment on consecutive days the gross behavioral changes and the vegetative symptoms failed to develop by the 3rd or 4th day. By that time the M U A changes of PH and M R F showed similar characteristics in response to T R H administration which was observed following the injection of desipramine and imipramine. The drugs, except for TRH, induced a suppression of paradoxical sleep cycles.

Abstract.

Thyrotropin-releasing hormone - Antidepressant agents - Brain stem - Hypothalamus Multiple unit activity - R E M sleep.

Key words:

been reported on the beneficial effects of T R H administration in mental depression (Kastin et al., 1972; Prange et al., 1972; Borsy et al., 1974; Drayson, 1974). An increasing number of publications demonstrate that the study of multiple unit activity (MUA) of subcortical structures provides detailed information on CNS mechanisms influenced by hormones (Barraclough and Cross, 1963; Beyer and Sawyer, 1969; Terkel et al, 1974, etc.). Guzmfin-Flores and his team elaborated an excellent technique for evaluation of M U A changes. It has been firmly established by this research group that the use of multichannel analyzers has several advantages in assessing objectively the behavioral stages and the activity level of the CNS (Guzmfin-Flores and Alcaraz, 1970; Beyer et al., 1971; Garcia-Castells and Guzm~n-Flores, 1972; Guzm~,n-Flores et al., 1972, etc.). This has been corroborated in other publications (Korfinyi and Beyer, 1971; Korfinyi and Guzmfin-Flores, 1973; Korfinyi et al., 1971 a, 1971 b; Korfinyi, 1973; Korfinyi and Liss~k, 1974; Tam~isy et al., 1975). The aim of the present work was the comparative M U A analysis of the effect of T R H and some tricyclic antidepressant agents, desipramine and imipramine on the neuronal behavior of mesencephalic reticular formation, area hypothalami posterior, and area hypothalami anterior.

INTRODUCTION A large number of antidepressant agents have been synthetized during the past decade. Research efforts in this field have recently revealed that the thyrotropin-releasing hormone (TRH), in addition to its effect on the hypothalamo-pituitary-thyroid axis, possesses CNS-influencing properties. Pros and cons have * Offprint requests should be sent to: Lajos Korfinyi, M. D., Institute of Physiology,University Medical School, H-7643 P6cs, Hungary.

METHODS Fifty-four experiments, lasting for 4 h each, were performed on chronically implanted freelymovingadult cats of either sex. Standard stereotaxicprocedure was used to implantchronicallycortical macro-, and subcortical semimicroelectrodes(nichromwire 62.5 g in diameter) insulated with enamel at the factory and cut to form uninsulated tip. In each animal the subcortical electrodes were aimed at the followingstructures: mesencephalicreticular formation (MRF), area hypothalami posterior (PH), and area hypothalami anterior (AH).

198 The method for simultaneous recording of EEG and M U A was basically that of Guzm~m-Flores and Alcaraz (1970). Briefly, the M U A of small neuronal pools of the subcortical structures were simultaneously analyzed. The neuronal spikes of a given height were chosen by means of a voltage gate, and an identical electronic window detector was used throughout the session for the same animal. The output of the spike discriminator was fed to a staircase generator and multivibrator system. This made possible the digital data processing of the firing rate of amplitude-discriminated cell discharges. During the hormone and drug studies gross behavior, EEG, and MUA were recorded continuously for I h prior to the injection and for 3 h after the treatment. In single injection studies at least 7 days elapsed between periods when the animal received a substance. The administered substances and doses injected intraperitoneally were as follows: thyrotropin-releasing hormone, TRH: 0.1, 0.3, 1.0 mg/kg (18 recordings on 6 cats); desipramine (Pertofran| : 0.3, 1.0, 3.0 mg/kg (6 recordings on 2 cats); imipramine (Melipramiu| : 0.3, 1.0, 3.0 mg/kg (6 recordings on 2 cats). In repetitive injection studies TRH in a dose of 0.3 mg/kg was administered for 6 consecutive days in 24-h intervals (24 recordings on 4 cats). At the end of experiments the animals were anesthetized with an overdose of pentobarbital, the brains were perfused with formalin solution, and removed for histologic control of electrode placements (Guzmfin-Flores et al., 1958). Student's t-test was used for the statistical evaluation.

Psychopharmacology 49 (1976)

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RESULTS

1. Effect of Single Injection a) Thyrotropin-Releasing Hormone. TRH injection resulted in slight or moderate changes in the gross behavior of the animals. This was characterized by intermittent somatic and vegetative symptoms, namely, restlessness, salivation followed by vomiting, miosis, hyperventilation, urination, and defecation. The vegetative excitation developed in 2 - 6 rain after the injection and lasted for 3 0 - 5 0 min. During the intermittently occurring gross behavioral changes the EEG was desynchronized and the M U A level was high. In quiet periods the EEG was characterized by slow wave activity similar to control spindle or slow wave sleep, but the M U A levels were variable in all structures. No correlation was found between the intensity and duration of somatic and vegetative symptoms and the administered doses in the same animal. The M U A analysis also failed to reveal clear dose-dependent relations of T R H action (Fig. 1). It is remarkable that T R H did not abolish the occurrence of paradoxiced sleep cycles (REM sleep). However, the latency of the development of REM sleep was significantly longer after the injection than during the control sessions.

b) Desipramine. The drug did not induce gross behavioral changes or vegetative signs. The desynchronized EEG was replaced by slow wave sleep in 1 0 - 1 8 rain following the injection. The action of the drug showed dose-dependent relation. The decline

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Fig. 1. Changes of amplitude discriminated cell discharges prior to (control) and following different doses of THR injection. Values (mean _+ S.E. of mean) after hormone administration represent activity recorded during slow wave sleep. Abbreviations: MRF, mesencephalic reticular formation; PH, area hypothalami posterior; AH, area hypothalami anterior; QW, quiet wakefulness; SWS, slow wave sleep

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of M U A reached the low level in 4 0 - 6 0 min, and remained stable until the end of the session. The M U A decrease in PH and M R F was highly significant (Fig.2). In spite of the increased duration of slow wave sleep, REM sleep failed to develop following desmethylimipramine administration.

L. Kor~inyi et al. : Effect of TRH on Multiple Units

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REM sleep was longer but the duration of paradoxical sleep cycles did not change as compared to the control periods. DISCUSSION

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Fig. 3. Effect of daily injection of 0.3 mg/kg TRH on MUA. Values represent activity recorded during SWS in course of repetitive TRH administration after 60 rain of injection. For abbreviations see Figure 1. Mean _+ S.E. of mean; P, 0.02; P, 0.01; P, 0.001

c) Imipramine. The gross behavior did not change after the injection. The desynchronized EEG was replaced by slow wave activity in ;10-15 min. Imipramine in a dose of 0.3 mg/kg did not result in significant M U A decrease and also failed to suppress REM sleep cycles. Higher doses completely suppressed REM sleep and the dose-dependent effect of the drug on subcritical M U A was found. Significant decline of activity was found in the PH and M R F which reached the low level in 5 0 - 6 0 rain, and remained stable until the end of the recording session (Fig. 2).

2. Effect of Treatment for 6 Days with TRH The animals were treated with a dose of 0.3 mg/kg T R H in 24-h intervals. Prior to each injection control EEG and M U A recording was made which was continued for an additional 3-h period after the treatment. Complete wakefulness and sleep cycles could be recorded during the control sessions. In the course of consecutive days the duration and intensity of the afore-mentioned somatic and vegetative symptoms showed a decline and eventually failed to develop by the 3 r d - 4 t h day of treatment. By that time the MUA decreasing tendency of the T R H effect became unequivocal. The effect of TRH on MUA manifested itself in the most significant decrease in the PH (Fig. 3). The latency for the development of

The effect and the trend of action of TRH on the central nervous system may depend on several factors. Earlier it was supposed that the activity of TRH on TSH-producing cells was highly specific. Several recent data showed that this small peptide, in addition to its modifying effect on hypothalamo-pituitary-thyroid axis, in one way or other, directly or indirectly, induced changes in other neuroendocrine mechanisms. It is known that TRH influences the production of growth hormone, the prolactin release, the DOPA activity, it results in changes of FSH and LH levels, and induces significant depression of stressinduced elevation ofpituitary-adrenocortical function, etc. These factors, in turn, may also influence CNS activity. It is evident that the effect of TRH on the CNS activity level cannot be considered to be the influence of a single factor but the action is the resultant of complex mechanisms (Lissfik, 1973; Zimmermann et al., 1973). Our findings that desipramine and imipramine induced a significant MUA decrease in PH and M R F are in agreement with earlier investigations. The observations according to which these drugs induce a suppression of paradoxial sleep cycles are also consistent with previous works (Bradley and Key, 1959; Kaneko et al., 1960; Vernier, 1961 ; Hishikawa et al., 1965; Hartmann, 1968; Wallach et al., 1969 a, b). The partial or complete suppression of paradoxical sleep cycles is generally considered as an undesirable effect of some CNS active substance. The fact that the TRH does not suppress REM sleep can be of major importance. It is difficult to explain the effect of single injection of TRH resulting diverse, nonuniform M U A and gross behavioral changes. The gross behavioral effects and the vegetative symptoms are possibly species-dependent (Borsy et al., 1974). Our present comparative M U A analysis revealed that following a few injections of T R H changes resulted similar to those induced by the single injection of some tricyclic antidepressant agents. The significant decrease of activity level in PH and M R F indicates that the agents investigated in this work through complex mechanisms exert a reducing effect on the function of the arousal system. Acknowledgement. Thanks are due to the Research Institute for Pharmaceutical Chemistry, Budapest, for the generous supply of synthetic TRH.

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REFERENCES Barraclough, C. A., Cross, B. A.: Unit activity in hypothalamus of the cyclic female rat. Effect of genital stimuli and progesterone. J. Endocr. 26, 339-359 (1963) Beyer, C., Almanza, J., de Ia Torre, L., Guzm~n-Flores, C. : Brain stem multi-unit activity during "relaxation" behavior in female cat. Brain Res. 29, 213-222 (1971) Beyer, C., Sawyer, C. H.: Hypothalamic unit activity related to control of the pituitary gland. In : Frontiers in neuroendocrinology, W. F. Ganong and L. Martini, eds., pp. 255- 287. London: Oxford Univ. Press 1969 Borsy, J., KirSly, I., Bajusz, S.: Behavioural and antidepressant effects of thyrotroph-releasing hormone, TRH. J. Pharmacol., Suppl. 5, 10 (1974) Bradley, P. B., Key, B. J. A. : A comparative study of the effects of drugs on the arousal system of the brain. Brit. J. Pharmacol. 14, 340 - 349 (1959) Drayson, A. M.: TRH in cyclical psychoses. Lancet 1974I, 312 Garcia-Castells, B., Guzm~in-Flores, C. : Percepci6n del ambiente. Bol. Estud. M6d. Biol. (M6x.) 27, 130 (1972) Guzmfin-Flores, C., Alcaraz, M. : A technique for recording and integrating unit activity. Bol. Estud. M6d. Biol. (M6x.) 25, 8 (1970) Guzmfin-Flores, C., Alcaraz, M., Fernandez-Guardiola, A. : A rapid procedure to localize electrodes in experimental neurophysiology Bol. Estud. M6d. Biol. (M6x.) 16, 29-31 (1958) Guzmfin-Flores, C., Garcia-Castells, E., Buchwald, N.: Las propriedades funcionalesyde la motoneurona como analizadoras de la actividad 61ectrica cerebral. Bol. Estud. M~d. Biol. (M6x.) 27, 133 (1972) Hartmann, E.: The effect of four drugs on sleep patterns in man. Psychopharmacologia (Berl.) 12, 346- 353 (1968) Hishikawa, Y., Nakai, K., Ida, H., Kaneko, Z.: The effect of imipramine, desmethylimipramine and chlorpromazine on the sleep-wakefulness cycle on the cat. Electroenceph. clin. Neurophysiol. 19, 518-52J (1965) Kaneko, Z., Hishikawa, Y., Shimizu, A., Fukui, S., Hidaka, Y.: Effects of imipramine on the electrical activity of the brain of the cat (in Japanese). No to shinkei (Tokyo) 2, 698-705 (1960) Kastin, A. J., Ehrensing, R. H., Schlach, D. S., Anderson, M. S.: Improvement in mental depression with decreased thyrotropin response after administration of thyrotropin-releasing hormone. Lancet 1972II, 740 Kor/myi, L. : Effects of adrenal steroids on brain function and behavior. In: Drug effects on neuroendocrine regulation, E. Zimmermann, W. H. Gispen, B. H. Marks, and D. de Wied, eds., Progress in brain research, Vol. 39, pp. 111-123. Amsterdam: Elsevier 1973

Psychopharmacology 49 (1976) Korfinyi, L., Beyer, C.: Effect of ACTH and adrenocortical hormones on brainstem multiple unit activity (MUA) during habituation and sleep-wakefulness cycle in the cat. XXV. Int. Physiol. Congress, Abstract, vol. IX. p. 317, Munich 1971 Kor~nyi, L., Beyer, C., Guzmfin-Flores, C. : Multiple unit activity during habituation, sleep-wakefulness cycles and the effect of ACTH and corticosteroid treatment. Physiol. and Behav. 7, 321-329 (1971 a) Kor/myi, L., Beyer, C., Guzmfin-Flores, C.: Effect of ACTH and hydrocortisone on multiple unit activity in the forebrain and thalamus in response to reticular stimulation. Physiol. and Behav. 7, 331-335 (1971b). Kor~inyi, L., Guzmfin-Flores, C.: Pituitary-adrenocortical hormone influences on multiple units in the brainstem and forebrain structures. In: Hormones and brain function. K. LissS.k, ed., pp. 427-436. New York: Plenum Press 1973 Kor~myi, L., Lissg.k, K.: Multiple units and responsiveness to sensory stimuli during maternal behavior. Pavlov J. Cond. Refl. 9, 178 (1974) Liss/tk, K. : Hormones and brain function. New York: Plenum Press 1973 Prange, A. J., Wilson, I. C., Lara, P. P., Alltop, L. B., Breese, G. R. : Effect of thyrotropin-releasing hormone in depression. Lancet 1972II, 999-1002 Tamfisy, V., Kortinyi, L., Liss/tk, K. : Multiple unit activity study of brain stem and limbic structures during environmental habituation and circadian rhythm. Pfl~gers Arch. 353, 361- 372 (1975) Terkel, J., Johnson, J. H., Whitmoyer, D. I., Sawyer, C. H. : Effect of adrenalectomy on a diurnal (circadian) rhythm in hypothalamic multiple unit activity in the female rat. Neuroendocrinology 14, 103-113 (1974) Vernier, V. G. : The pharmacology of antidepressant agents. Dis. nerv. Syst. 22, 7 - 1 3 (I961) Wallach, M. B., Winters, W. D., Mandell, A.J., Spooner, C. E. : A correlation of EEG, reticular multiple unit activity and gross behavior following various antidepressant agents in the cat. Electroenceph. clin. Neurophysiol. 27, 563-573 (1969a) Wallach, M. B., Winters, W. D., Mandell, A. J., Spooner, C. E.: Effects of antidepressant drugs on wakefulness and sleep in the cat. Electroenceph. clin. Neurophysiol. 27, 574-580 (1969b) Zimmermann, E., Gispen, W. H., Marks, B. H., de Wied, D. : Drug effects on neuroendocrine regulation. In: Progress in brain research, vol. 39. Amsterdam: Elsevier 1973

Received February 2, 1976; Final Version May 18, 1976