ALTERATIONS I N GABA METABOLISM AND MET-ENKEPHALIN CONTENT IN RAT BRAIN FOLLOWING REPEATED ELECTROCONVULSIVE SHOCKS A. R. GREEN', E. PERAL-IA', J. S. HONG.C. C. MAO, C. K. ATTERWILL3 and E. COSTA Laboratory of Preclinical Pharmacology, National Institute of Mental Health. St. Elizabeths Hospital, Washington. D.C. 20032. U.S.A. (RL~ruirrdI I Junrrury 1978. .Accepted 21 March 1978) Abstract- Thc effects of electroconvulsive shock (ECS; 12OV for 1 s through ear-clip electrodes) or sub-convulsive shocks (70 V for 1 s) on rat brain G A B A and met-enkephalin concentration and G A B A turnover has been examined 24 h after a single treatment ( x 1) or once daily for 10 days ( x 10). ECS x 10 increased G A B A concentrations in the N. caudatus and N. accumbcns and decreased the synthesis rate of G A B A by 40:" and 500; respectively in these regions. Sub-convulsive shocks ( x I0 x 10) or ECS x I had no effect. No consistent changes were seen in thc substantia nigra. Met-enkephalin concentrations increased by 50"" in the N. caudatus after ECS x 10 but were unchanged in the cortex and pons:medulla. No other shock regimen had any effect on the concentration of this peptide. The results are discussed in relation to the enhanced monoamine-induced responscs seen only after ECS x 10

ADMINISTRATION of repeated electroconvulsive shock to rats (ECS) (normally one shock daily through earclip electrodes for 8- 10 days) results in them displaying enhanced behavioural responses to tranylcypromine and L-tryptophan administration, a drug procedure which increases 5-HT synthesis and 'spill over' into functional activity (EVANSct a/., 1976). The behavioural responses t o the putative 5-HT agonist 5-methoxy N,N-dimethyltryptamine is also increased by ECS pretreatment (EVANSrt ul., 1976) suggesting an enhanced post-synaptic 5-HT response. Both dopamine and noradrenaline mediated behavioural responses are also enhanced by ECS pretreatment and experiments with agonists indicated that these enhanced responses are due to increased catecholamine post-synaptic responses (GREEN rt a/., 1977: MODIGH,1975). Such changes are not produced by rt a/., 1977) but can sub-convulsive shocks (GREEN be elicited by flurothyl, a n inhalant convulsant (GREEN,1978) demonstrating the importance of the convulsion. Furthermore, when the ECS is given in ways which mimic closely the clinical administration of electroconvulsive therapy (ECT), the same increase in postsynaptic 5-hydroxytryptamine induced behaviour occurs (COSTAIN rt a/.. 1978) and this has led to the t Permanent address: MRC Unit of Clinical Pharmacologj. RadcIitTe Infirmary, Oxford OX2 6HE. England. ' Grantee of the Program for Cultural Co-operation between the United States and Spain. MRC Unit of Clinical Pharmacology, Radcliffe Infirmary, Oxford, England. Ahhreciurions used: ECS. electroconvulsive shock: ECT, clectroconvulsive therapy; ME. met5-enkephalin.

suggestion that ECT might be producing its therapcutic action by increasing monoamine post-synaptic responses (GRAHAME-SMITH rt a/., 1978). O n e reason for changed monoamine-mediated behavioural responses could be a reduction in the modulatory influence of neurotransmitters or neuroregulators thought to be normally inhibitory in action. In brain structures innervated by monoaminergic neurones such as striatum and N. accumbens. y-aminobutyric acid (GABA), and met5-enkephalin (ME) (HONGr t a/.%19776; YANC rr ul., 1977; 1978) neurons seem worthy of particular attention. Some of the behavioural models used in the initial investigations on ECS (the hyperactivity following tranqlcypromine plus L-tryptophan or L-DOPA or the locomotor activity following methamphetamine or apomorphine) can be modified by alterations in brain r t a/., 1976; COTT& E N G ~ L . GABA content (GREEN 1977). Furthermore. GABA is intimately involved in convulsive behaviour (see review by ROBERTS,1975) as shown by the anti-convulsive action of muscimol (NAIKet a/., 1976) and by the convulsions that are associated with a decrease of brain GABA content. Recent evidence has suggested that the high concentrations of M E present in striatum are associated with intrinsic striatal intcrneurons (HoNG c't a/..1977; YANGc't a/., 1978) which form axo-axonic synapses rr a/.. 1977). with dopaminergic axons (POLLARD The investigation of GABA function has recently been much improved by the development of a massfragmentographic method which allows not only the measurement of endogenous glutamate and GABA in discrete nuclei of rat brain but also the turnover rate estimation of GABA (BERTILSSON & COSTA,1976; BrRnLssoN er a/.. 1977) and this has been used suc-

607

A. R. GREENet al.

608

cessfully t o study the pharmacological actions of several drugs o n GABA metabolism (MAO er al., 1917a; 1978; MARCOet a/.. 1976). The ME content of various brain nuclei can also be measured by the radioimmunoassay as reported by Y A w rt a/. (1977). We have therefore investigated the effects of repeated ECS on met-enkephalin and GABA content and GABA turnover in rat brain nuclei in which dopamine is considered t o play a neurotransmitter role and be involved in the behavioural responses previously observed to be modified by ECS. Results have been compared with the effects of repeated subconvulsive shock or a single ECS. METHODS

dissolved in ethyl acetate and a small aliquot was injected into the gas chromotograph-mass spectrometer (LKB 9000, with multiple ion detector). Separations were made on a column (3"j, OV-17 on Gas-Chrom Q ) at 13O'C. The following fragments were analysed using the multiple ion detector: rn/e 398 from endogenous glutamic acid; m/e 400 from ['3C]glutamic acid; cn/e 403 from glutamic acid-D,: inje 399 from endogenous GABA; IJI/C' 401 from ["CIGABA; and ni/r 413 from 5-amino-11-valeric acid. The peak height ratio of glutamic acid/glutamic acid-D, and GABA/amino-n-valeric acid were plotted against standard curves for endogenous GABA and glutamate concentrations and peak height ratio of !n/e values 400/398 and 401/399 measured the incorporation of "C into glutamate and GABA, respectively. Full details of the methods and turnover rate calculations are given in the papers of BERTILSSON & COSTA(1976) and BERTILSSON er al. (1977). Protein was measured by the method of LOWRVet a/. (1951). Measurernent of inet-enkephalin. Punched out brain nuclei from 400 pM-cryostatic sectioned brain slices from rats killed by microwave irradiation were extracted with 0.1 N-acetic acid. The extracts were neutralized with 1 N-NaOH and radioimmunoassayed for ME as described by YANC et al. (1977) with an antiserum directed toward ME which cross reacted with leu-enkephalin by less than 10%. Statisrical ecaluation ofrhe data. The statistically significant differences in the content of glutamate, enkephalin or GABA and in k,,,, and turnover rate of GABA (TRGAB,)of various brain nuclei was determined by the Dunnett's test (two tailed) corrected for unequal sample size (WINER,1971).

Genurul. Male Sprague-Dawley rats (Zivic-Miller, Allison Park. PA) initial weight 80-90g were used. Five groups of rats that were examined: one given no treatment (control). a group given one convulsive shock daily for 10 daqs (ECS x lo), a group given a sub-convulsive shock daily for 10 days (sub-con x lo), a group given one convulsive shock (ECS x 1) and a group given one subconvulsive shock (sub-con x I). In all cases. measurements were made 24 h after the final convulsive or subconvulsive shock. Shocks were delivered from an Edison portable electroshock machine through ear-clip electrodes (EVANSet al., 1976). Convulsive shocks were 120 V and sub-convulsive were 70 V. In both cases. the pulse was sinusoidal (60 Hz) for 1 5 . ~ 4 ~ ~ u s i ~ r e i o~fi eGnAt B A iiiernholisrn. Twenty-four hours following the last ECS treatment the rats were infused for IOmin into the tail vein with 1)-glucose (50pmo1,kg per RESULTS min) uniformly labelled with I3C (isotopic enrichment Eflect of ECS on brain gluturnate and GABA concen75-80",, Merck, Sharpe & Dohme. Montreal) at a constant trations rate of O.IOml/min. At the cnd of the infusion the rats It was found that 2 4 h after 10 daily ECS or a were killed by exposure of the head for 4 s to a focussed ECS there was no significant changes in the high intensity microwave beam as described by G ~ ~ I D O T Tsingle I er a/. (1974). Brains were rapidly removed and frozen on glutamate content of the N. accumbens. N. caudatus dry ice. The frozen brains were sliced ( 4 0 0 ~in~ a) cryostat or substantia nigra, except possibly a small rise in at -4'. Various brain nuclei were punched out using a N. accumbens after ECS x 10 and the striatum after hollow steel tube with an inside diameter of 0.8 mm (Kos- ECS x 1. There were, however, marked changes in LOW c'r a/.. 1974). The punched sample generally contained the GABA content of the brain structures studied between 40 and 8 0 p g protein. (Table 1). It was seen that ECS x 10 increased the The punched tissue was homogenized in loop1 of 80% GABA content in both the nuclei accumbens and cauaqueous ethanol containing the internal standards. The internal standards were L-glutamic 2,3.3,4,4,-D5acid (M.S.D.) datus while a single ECS or single or multiple subconvulsive shocks were without effect (Table 1). In the for glutamate and 5-amino-n-valeric acid HCI (K & K Labs) for GABA. Pentafluoropropionylamide hexafluoro- substantia nigra there was no clearcut effect insofar a s all treatments appeared t o cause a small but insigpropyl esters of GABA, glutamic acid and their internal standards were formed. After evaporation, the residue was nificant rise in GABA. TABLEI . TISWEGLUTAMATE

N. accumbens Glutamate GABA Control ECS x 10 Sub-con x 10 ECS x 1 Sub-con x I

87 115 96 99 89

&8 & 11* i5 f4 f5

48 f 4 79 f 10: 48 f 3 51 f 4 44f4

AND

GABA

CONCENTRATION

(nmol/mg

N. caudatus Glutamate GABA

116 102 99 132 121

f3 &6 f8 f7 f3

25 k 1 31 f 4t 24 f 2 23 f 2 24 k 2

PROTEIN)

Substantia nigra Glutamate GABA

54 f 7 44 f 4 61 f 6 93 f 8 76 f 7

73 f 5 112 f 2

96 f 6 91 k 5 92 f 9

* P < 0.05; t P < 0.01 ; :P < 0.001 when compared to untreated rats with results from 4 to 7 determinations Results shown as mean f 1 S.E.M. For experimental details of shock administration see Methods section. ECS: electroconvulsive shock; sub-con: sub-convulsive shock.

GABA turnover and electroconvulsive shock

TABLE 2. GABA

FRACTIONAL RATE CONSTANT

(kGABA/h) A N D GABA

TURNOVERRATE VARIOUS TREATMENTS

Control ECS x 10

Sub-con x 10 ECS x 1

Sub-con x 1

24 f 3 12 f 2* 26 f 1 27 f 2 27 f 2

(TR,,,,

nmol/ng PROTEIN^)

N. caudatus

N. accumbens kCiA8A

609

TRGABA 1152 948 I248 1377 1188

Substantia nigra TRGARA

ThBA

b A B A

17 & 1.3 11 f 1.ot 17 f 1.2 19 f 5.0 21 f 7.0

408 319 340 437 504

AFTER

~ C A B A

10.1 f 2.0 6.6 f 0.2 8.5 f 0.6 11.7 f 4.3 7.1 2 0.6

Different from untreated control * P < 0.01 ; tP < 0.001. Results from 4 to 7 determinations and show mean f S.E.M. TR,,,, obtained by multiplication of k,,, tration of GABA. For experimental details of shock administration see Methods section. ECS: electroconvulsive shock; sub-con: sub-convulsive shock.

730 739 816 1092 653 with concen-

Effect oJ ECS on the turnorer rate of G A B A in nuclei accuinhens and caudatus and substantia nigra

turnover measurements probably reflect GABA utilization at the nerve endings and this view is supported Studies on the fractional rate constant (kGABA)by experiments in which electrical stimulation (0.5 ms, obtained by measuring the rate of incorporation of 20 Hz, 8 V) of the nucleus caudatus caused an increase of substantia nigra (MAOet a/., 1978). 3C]glucose into glutamate and GABA again in TR,,,, However, as with any turnover measurement the revealed that 10 daily ECS produced changes in measurements depends on the k,,, (Table 2) that were not seen after either a single reliability of TR,,,, verification of a set of assumptions. That having been ECS or single or multiple sub-convulsive shock was decreased by approximately 50% said, it is clear that the results reported in Table 2 (Table 2). k,,, in the N. accumbens and 40% in the N. caudatus are valuable for comparative purposes, although they following ECS x 10. Again, the substantia nigra was may not reflect absolute measurements of GABA et a[., 1977). different in that no consistent changes in k,,, were turnover (BERTILSSON With regard to the GABA studies, it is apparent seen. Table 2 also shows that TR,,,, in N. accumbens and N. caudatus of rats killed 24 h after that repeated ECS cause changes in both GABA conthe last of 10 ECS is smaller than that of the same centrations and turnover while all other treatments brain nuclei of control rats or those receiving 10 sub- (subconvulsive or ECS x 1) have little effect. This is interesting since of all the schedules examined in this convulsive shocks. study it is only ECS x 10 which produces enhanced Effects of ECS on inet5-enkephalin content in various monoamine-induced behavioural responses (EVANSet brain regions al., 1976; GREENet al., 1977; GRAHAME-SMITH et al., Single or repeated ECS or sub-convulsive shocks 1978). The decrease of TRGABAwas seen in N. had no effect on the ME content of the cortex or accumbens and N. caudatus but not in the substantia pons/medulla. However, ECS x 10 produced a 50% nigra. Perhaps this indicates that the reduction of rise in ME content of the N. caudatus. It was again TRGABA is not due to a generalised change in GABA observed that it was only the ECS x 10 that had any metabolism due to a non-specific action of ECS on effect, a single ECS or single or repeated sub-convul- enzymes involved in GABA metabolism. ECS apparently elicits specific changes in GABA afferent sive shock produced no change at all (Table 3). neurons intrinsic to N. accumbens and N. caudatus, but not to the long axon GABAergic neurons of the DiScUSSiG.N. strionigral pathway. In mammalian brain, a major site for GABA synIt does not seem unreasonable to suggest that the thesis is considered to be located in the axon ter- raised GABA content together with the decrease in minals since glutamic acid decarboxylase (GAD) is synthesis rate (kCABA) leads to a decrease in TRGABA concentrated in these sites (Woon et al., 1976; BARBER because the decrease in kCABA over-compensates for & SAITO,1976). It has been suggested therefore that the increase in GABA content. When there is a de-

[’

TABLE 3. EFFECTSOF Region N. caudatus

Cortex Medullaandpons

ELECTROCONVULSIVESHOCK ON THE MET-ENKEPHALIN CONTENT I N VARIOUS BRAIN REGIONS

Control

ECS x 10

9.5 & 0.74 0.50 f 0.050 2.5 f 0.30

16.0 f 0.90* 0.62 f 0.070 2.6 f 0.40

Sub con

x

10

9.9 f 0.85 0.45 f 0.060 2.2 0.30

ECS

x 1

9.5 f 1.0 0.52 f 0.060 2.0 f 0.20

Sub con x 1

9.3 f 1.2 0.60 f 0.040 2.6 f 0.40

Met-enkephalin content is expressed as ng/mg protein. * P < 0.05 compared to control rats. For experimental details of shock administration see Methods section. ECS: electroconvulsive shock; sub-con : sub-convulsive shock.

610

A. R. GREEN et al.

In summary, therefore, it is possible that the crease in the synthesis of a transmitter and an increase in its concentration it is always indicative of observed changes in GABA turnover and ME concena decreased release and probably a functional reduc- tration in nuclei caudatus and accumbens are responsible for the enhanced dopaminergic behavioural retion of GABAergic transmission. If ECS x 10 has indeed lowered the inhibitory tone sponses seen after repeated ECS. Whether these in the GABA-ergic interneurons of the N. caudatus changes are relevant to the antidepressant action of and N. accumbens, then prcsumably the inhibition ECT can only be speculated on at present (GRAHAMEin these neurons, which appear to be post-synaptic SMITHet al.. 1978). to dopaminergic neurons (MAOet al., 1977b), has been reduced by ECS. From these considerations one Acknow/edyc.rririirA. R. GWEN thanks the Medical might infer that post-synaptic dopamine behavioural Research Council (U.K.) for the provision of travcl funds. responses might be enhanced after ECS x 10 and this is indeed what is seen (EVANSet al., 1976; GREEN REFERENCES er a/.. 1977; MODIGH, 1975). The observation that changes in GABA function appear to occur in the B A R B ~R.R& SAITOK . (1976) Light microscope visualization of GAD and GABA-T in immunocytochemical N. accumbens is interesting in view of the role this preparations of rodent CNS. In G A B A iri Nerrous SJSarca plays in the production of amphetamine-induced ten1 Function (ROBERTSE.. CHASE T. N. & TOWFRD. B.. locomotor activity (KELLYet a/., 1975) and the fact eds.) pp. 113-132. Raven Press, New York. that amphetamine-induced locomotion is increased BERTILSSON1.& COSTAE. (1976) Mass fragmentographic et ul., 1977). Injection of dopamine after ECS (GREEN quantitation of glutamic acid and 7-aminobutyric acid into this area also produces locomotor activity and in cerebellar nuclei and sympathetic ganglia of rats. J . this activity is increased following ECS (Heal & Chroniar. 118. 395-402. Green, unpublished observations). Furthermore, BERTILSSONL., MAOC. C. & COSTAE. (1977) Application of principles of steady state kinetics to the estimation dopamine mediated activity produced by discrete inof p-aminobutyric acid turnover rate in nuclei of rat jection into this area is inhibited by increasing brain brain. J . Pharinac. e s p . Ther. 200, 277-282. GABA content by pretreatment with amino-oxyacetic COSTAIN D. W., GRAHAME-SMITH D. G. & GREEN A. R. acid (HEALet a/., 1978). (1978) Relevance of the enhanced 5-hydroxytrqptamine At present, it is difficult to interpret the observabehavioural responses in rats to electroconvulsivc thertions on ME because it is not known whether an apy. Br. J . Pharmuc. 62. 394. increased content reflects a decrease in the utilization COTTJ. & ENCEL J. (1977) Suppression h) GABAergic rates. However. assuming that the content of the drugs of the locomotor stimulation induced bq mortransmitter also increases when its release and funcphine, amphetamine and apomorphine: evidence for tion is decreased, we could also infer that the increase both pre- and post-synaptic inhibition of catecholamine systems. J . Neural Trans. 40, 253-268. in the enkephalinergic striatal neurons is associated D. G.. GREENA . R. & with a dopaminergic facilitation. Enkephalins modu- EVANSJ. P. M., GRAHAME-SMITH TORDOFF A. F. C. (1976) Electroconvulsive shock inlate dopaminergic systems in an inhibitory fashion via creases the behavioural responses of rats to brain 5-hydet al., 1977) and thus, axo-axonic synapses (POLLARD roxytryptamine accumulation and central nervous sysa decrease of this control may be relevant to the intem stimulant drugs. Br. J . Pharoiac. 56, 193-199. creased behavioural responses t o dopamine receptor GRAHAME-SMITH D. G., GREENA. R. & COSTAIN D. W. activation following ECS x 10. (1978) Mechanism of the antidepressant action of elecA major problem with assessing the data obtained troconvulsive therapy. Laiicer i. 254-257. is that of knowing which changes are primary and GREEN A. R. (1978) Repeated exposure of rats to the conwhich arc secondary. This is, whether the enhanced vulsant agent flurothyl enhances 5-hydroxytryptamlne and dopamine mediated behavioural responses. Br. J . catecholaminergic responses are the result of a Pharinuc. 62, 325-33 1. changed TR,A,A or whether GABA changes because GREEN A. R., HEALD. J. & GRAHAME-SMITH D. G. (1977) of altered dopamine function. Further observations on the effect of repeated electroIn this regard i t has been shown that changes in convulsive shock on the behavioural responses of rats dopamine turnover following dopamine receptor produced by increases in the functional activity of brain blockade fails t o alter GABA turnover in the striatum 5-hydroxytryptamine and dopamine. Psychopharniacobut facilitates it in the N. accumbens (MAO et al., logy 52, 195-200. 1977a, b). However, repeated ECS changes neither GREEN A. R.. TORDOFF A. F. C. & BLOOMFIELD M. R. (1976) dopamine nor 5-HT synthesis and we therefore tentaElevation of brain GABA concentrations with aminotively suggest that the GABA changes seen after ECS oxyacetic acid; effect on the hyperactivity syndrome produced by increased 5-hydroxytryptamine synthesis in may not therefore be secondary to a change in doparats. J . Neural Trans. 39, 103-1 12. mine neurones. GUIDOTTI A,, CHENEY D. L., TRABUCCHI M.. DOTEUCHI M.. It is certainly possible that both GABA and dopaWANGC. & HAWKINS R. A. (1974) Focussed microwave mine function change because of a primary change irradiation: a technique to minimise post-mortem in M E function and it is tempting to speculate that changes of cyclic nucleotides. DOPA and choline and ECS relieves depression and changes neuronal functo preserve brain morphology. Neuropharniuco/oyj 13. tion by primarily modifying the M E system. 11141121.

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61 1

E.. MORONIF. & COSTAE. (1978b). HEALD. J., PHILLIPS A. G. & G R ~ I A. N R. (1978) Studies MAOC. C., PERALTA The turnover rate of gamma-aminobutyric acid in the on the locomotor activity produccd by injection of dibusubstantia nigra following electrical stimulation or tyryl cyclic 3'5' AMP into the nucleus accumbens of rats. lesioning of strionigral pathways. Brain Res. in press. Nrurophartnacology 17, 265-270. HONGJ. S.. YANG H.-Y. T. & COSTAE. (1977a) On the MARCOE., MAO C. C., CHENEYD. L.. REVUELTAA. & COSTAE. (1976) The effects of antipsychotics on the turnlocation of methionine enkephalin neurons in rat striaover rate of GABA and acetylcholine in rat brain nuclei. tum. Ntwophartnacology 16, 451453. Nature 264, 363-365. HONG J. s., YANG H.-Y. T., FRAIIA w. & COSTAE. (19776). Determination of methioniine cnkephalin in dis- MODIGHK. (1975) Electroconvulsive shock and postsynaptic catecholamine effects: increased psychomotor stimucrete regions of rat brain. Brain Rrs. 134, 383-386. lant action of apomorphine and clonidine in reserpine P. W. & IVERSEN s. D. (1975) KELLYP. H..SEVIOUR pretreated mice by repeated ECS. J . Neural Trans. 36. Amphetamine and apomorphine responses in the rat fol19-32. lowing 6-OHDA lesions of the nucleus accumbens septi and corpus striatum. Brain Rrs. 94. 507-522. MODIGHK. (1976) Long term effects of electroconvulsivc KOWLOWS. H., RACAGNI G. & CosrA E. (1974) Mass fragshock therapy on synthesis, turnover and uptake of mentographic measurement of norcpincphrine, dopabrain monoamines. Ps~~chopharniacolog~ 49, 179-185. A. & COSTAE. (1976) Central GABA mine, serotonin and acetylcholine in seven discrete nu- NAIKS. R., GLIIDOTTI receptor agonists: comparison. of muscimol and bacclei of the rat teldiencephalon. Nruropliur~iiacology 13. 1123-1 130. lofen. Neurophrrnt~aco/ogj~ 15, 479484. LOWRY0. H., ROSEBROUGHN. J.. FARRA. L. & RANDALL POLLARD H., LLORENS-CORTES C. & SCHWARTZ J. L. (1977) R. J. (1951) Protein measurement with Fohn phenol reEnkephalin receptors on dopaminergic neurones in rat agent. J . hiol. Chetn. 193, 265S275. striatum. Nature 268. 745-747. MAO C. C.. CHENEY D. L., MARCOI.,REVUELTA A. & ROBERTSE. (1975) y-Aminobutyric acid and nervous system COSTAE. (1977a) Turnover times of gamma-aminobufunction- a pcrspcctivc. Biochrtn. Pharmuc. 23. tyric acid and acetylcholine in nucleus caudalus, nucleus 2637-2649. accumbens. globus pallidus and substantia nigra effects WINERR. J. (1971) in Statistical Principles in Exprritnrnrd of repeated administration of halopcridol. Brain Res. Design, 2nd ed. McGraw-Hill, New York. 132, 375-379. B. J. & VAUGH J. E. (1976) WOODJ. G.. MCLAUC~HLINE A BFRTIL MAO C. C.. MARCOE., R ~ V U E L T A,. Immunocytochemical localization of GAD in electron COSTAE. (1977h) The turnover rate of y-aminobutyric microscopic prcparations of rodent CNS. In GABA in acid in the nuclei of teiencephalon: implications in the Nercous Systrni Fimction (ROBERTS E., CHASET. N. & pharmacology of antipsychotin and of a minor tranquiTOWERD. B., eds.) pp. 133-148. Raven Press. New York. lizer. Biol. Psychiat. 12, 359-371. YANG H.-Y. T., HONGJ. S. & COSTAE. (1977) Regional MAOC. C., MARCOE.. REVUELTA A. & COSTAE. (1978~) distribution of leu- and met-enkephalin in rat brain. Neurophartnacology 16, 303-307. Antipsychotics and GABA turnover in mammalian brain YANG H.-Y. T.. HONGJ. S.. FRATTA W. & COSTAE. (1978) nuclei. in Interactions hrtwern Pirtuticr NeurotransRat brain enkephalins: distribution and biosynthesis. mirrrrs. pp. 151-159. Raven Press. New York. Ada. Biochem. Psychopharniac. 18, 149-1 59.