ABSTRACTS

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ELECTROPHYSIOLOGICAL KAtiIFESTATIONS OF SUPRASPINAL ACTIONS OF BACLOFEN. H.-R. Olpe. A. Glatt and W. Bencze. Research Dept., Pharmaceuticals Divisic”, CIBA-GEIGY Ltd..Basle,SHitrerla”d. hlicrciontophoretically applied Baclcfe” (B) potently depres- ses the spontaneous discharge rate of different types of “eu- rc”s in various areas of the rat brain such as the dopamine “e”rc”s, the majority of thalamic and “eocortical “eurcns. The physiological processes which produce this effect are not know”. We perfarmed a structure-activity study a” the cell and reflex depressant action of a variety of B-derivatives. Eve” small structural changes of the GABA-moiety were accompanied by significant reductions of the cell depressant and reflex reducing action. These findings suggest that the activity of B does “ct reside only within the phenylethylamine mciety of B alone as suggested previously. Recent biochemical and elec- trcphysiclcgical data suggested that B acts through inhibition of the release of glutamate. In doses of 10 q/kg i.p. B did “ct attenuate the cortically evoked excitations of striatal cells which are thought tc be mediated through glutaminergic fibers After systemic application we could denonstrate central ef- fects at the single cellular level as hell as by means of electrcencephalcgraphic investigations. In doses of 3-10 mglkg i.p. B inhibits the spontaneous discharge rate of dopaminergic neurons in AP and A10 and of neurons in the dorsal raphe “ccl0 US. In the freely moving cat 3.0 mg/kg p.0. B completely dis- organized the sleep-waking patter” and high delta waves ap- “eared on the ECG.

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REGIMAL GASA roxEFTOR MANGE8 FOLKWING A ccN”uLsIoN. Eric J. Essnan pnd Walter 8. Essman. Queens College of the City University of N.Y., Flushing, N.Y. 11%).

GABA has been implicated in the regulation of seizure activity and the maintenance of anticonvulsant mechanisms; it was cur purpose to examine the changes in GABA receptor affinity in rat brain and to define changes at these sites-- produced by a single convulsion in the rat. Synaptosomes were prepared from freshly excised cerebral cortex, dien- cephalon, and cerebella cortex of rats et several times (0 to I80 min.) after a single clonic-tonic convulsion. The uptake of C”‘GABA by these regional synaptoscmes ~85 measured, and its crganelle disposition was assessed. After the convulsion GABA uptake was decreased. This was noted after 60 min. for diancephalic and cerebellar “ewe endings (54% Bnd 43%. respectively; vO.05) and maximal reduction occurred at these sites at 2 hrs. after the convulsion (42% and 58%. respectively; pcO.01). GABA uptake was assc- ciated with the membrane fractions; this effect was “0 longer apparent by 3 brs. post-convulsion. The specific binding of GABA to regional me&vane receptor sites was significantly increased (2 to S-fold) during the “short” post-ictal phase (20 min.)--but not affected during the “long” post-ictal phase. This effect was noted for dien- cephalic and cerebellar cortical tissue, but not for the cerebral cortex. Ihe post-iota1 disposition of GMA de- pends upon a temporal sequence within which receptor af- finity and nerve ending disposition are regionally altered.

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EFFECTS OF GASA AGONISTS AN0 ANTAGONISTS ON ACT” RELEASE. G. Keith Matbeso", Indiana "niversity School of Medicine, P.O. Box 3287. Eva”sville, Indiana 47732. Gamma-amincbutyric acid (GABA) has bee” detected in the hypothalamus; and (‘H) GABA has bee" found to bind to hypothalamic postsynaptic melnbrane fractions. Amonget ite many functions the hypothalamus reguletes the release of eorticotrcpi” (ACTH)frcm the puititary glsnd. Since OABA ie a reputed inhibitory “eurotransmitter it was of interest to test the effects of GABA agonists and anta- gonists on ACTH release, as measured by glucocorticoid levels. Thirty seconds of handling stress followink! a" injection of saline (i.p) elevated cortieostercne levels in the rat to 42.65Hs.74 (S.L.6) after thiIty minutes. If the animals were injected with the GASA analog baclofe" (2mSlkS) in lieu of saline the cortieosterone levels were 10.90f1.74 (10). I" the cat, ACT,, release is facilitated by electrical stimulation of the basalateral amyygdala, picrctoxin or bicuculline injection, or sodium pentcbmbical injection. Baelofe" also prevented these stimuli from eliciri"S a" increase in ACTH release. Since GASA is k"nom LO act both pre- and post-syoa~tically. the effect of baclofen and bicuculline on tonic d.e. potentials in the hypothalamus was studied. Sicucul- line generated a negative (byperpolarizi"S) shift in the d.c. potential while baclofe" elicited a positive (depolarizi"S) shift. This would indicate that bicuculline and baclcfen are actinS, in the main, pre-synaptically.

GABA Am rl”oDENAL ULCEIUTION: PBRIPHERU AND/OR mnTRA.i. Ih”l’ERI\cTIONs. Sandor Szebc and Heidi C. “crnsr. OePts. of Pathology, peter Bent Brigham AoeP., “ward “ed.. Sch., Boetc”, MA 02115, U.S.A.

A few *ears ego we developed models of chemioallyi”d”ced duodenal ulceration in T&S. scructure-acti”ity relation- ship among these chemicals suggested that certdi" "euro- transmitters might have a role in the w&oge"esis Of this disease. Our recent "europharmacologic and bioehwical ex- periments revealed that dowine aqcnists and antzqoniste are anti- aI.3 pro-"lcerogsns, respectively, in these disease models. I" the present *tudies, ve investigate.3 the role of GABA and related drugs in the dem,lo~e"t of chemically in- duced ducdenal ulceration. Pemak., 2oc.g Sprague-Daxley- derived Charles River rats were pretreated with Sta"dArd ~balmacoloqic doses of direct ,m"scimol, or indirect WLBA

- CC-acetylenic GABr.,r-vinyl GAEA) , or direct (bi- picrotoxi”) or indirect GlieA ~tegcoiet (allyl-

The animals the” received cysteamine (2Eaq/lOCq p.0. x3, with 3 br intervals) and the swi~rs were sacri- ficed 2 days later. The GsBA agoniets aggra”eted the inci- denoe and intensity of experimental duodenal ulcer ee well as the q ortalitv. while GABI\ antaoo”is&exerted a” anti- . “lcercge”ic action. Mea*“remenr b; s*ctrofl”crim*tric me- thod of GABI ccncentratione in the brain, glandular and forestamach, dccdencm and edre”a1 revealed tbet an ulcera- genie dose of cysteanine or Propionitrile decreased -A levels to 791 or 81%. respectively, in 4 br in the *dre”els, 88% or 87. in the forestcmach. pence, G?&A and MB?.-related drugsmight mcdu1ats duodenal ulceration.

P Felts, PM Seadley 6 F &“tangelo, Iab phyalol den C&tres Aerveux, Univ P dr N Curie, 4 Place Jusaie”, 752% Paris

I”bibitio” of either neuronal or glial GBBA uptake 08” en- ha”oe responses to exogenous GABA but it appears not to af- feet GAMergic synaptic inhibitiona (Iom, Johllato”, Curtis k &e.“d, 1977, Brain Rea 136, 51J; Brow” 61 Calvpn, 1977, Brit J pharmao 54, 373). To investigate em aspecta of this dichotomy we have recorded GABA msponaes of neumnes in DRG, where GAaA uptake ie exclusively &al.

Pats (6O-12Og) wire stuned and killed snd DRG were rapidly excised, pinned in a simple ohamber on 9.a stage of a microscope and euperfused vl+,b

“i” ratw35c. Intre-

cellular (@I KAc) and iontqhoretic 1H GA@ pipettes were positioned i”/near surface oelle cnder direct vi& control. Short iontophoretic or b&b admFnistratio”e of GdBll elicited depolarizing reopo”eee tich wen not snbanced (but were eonetinee reduced) during inhibition of GABA uptake by ,G-30

min auperfusi0na 0f manine itif, chl~rpr=u 0.25&l O= s*ro sodium (Trie-litbicm). &I the other hand preliminary eqerimants &we Ohovn that (a) Gmltice11ular surface potential reeponees of IIRG to GABA are enhanced by uptake inhibition (D A Bmvn B H Deewae”i~ and (b) ponetratio” of (Z)GBBB into IlEG is greater du,,q uptake i”hibitic” (autoradiography by P Peltz k G Id&. T&en together thee= reeolts sudgest that @ial GABA uptab doee modify GABA diffllsion t&a@ tissue but does not affect the res- p-es of “ecxc”es olose to the source of GABA.

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GA&. IMUBITIQN OP N-MYDNL-ASPARTATE STIMIA’IEII IUEINI- ZING HCRMINE RELEASE. J.W. OIr~ey and M.T. Rice. Wash. univ. Sch. Med.. Eeut. pSy&iat.. St. Louis. MO 63110.

r&en * non-t&it-dose Q5 mg&) of the ileurcacitatcly amino acid, Kroethyl aspartate (N&4) is administered sc to 25 day old male rats, serwl levels of luteiniain& ho- (w rise 8-10 fold. lhe IH respxw? is rapid (within 7ir min), brief (30 ndj~ duraticn) and reversible. It is depen- dent on the integr-ity of ar~uate hypothalamic (AH) neumns and is swrase11ari since NM does not release LH in Ml-le- sioned rati nor f&n pituitary in vitro. Mi4, rhi& has ac- cess to &I !xumns fran blood r& lies outside blood brain barriers), selectively destroys AH newas when given in sufficient dose (75 r&g SC). lSz have pmposed that both the toxic and Wreleasing actions are mdiated by an exc.itatoIy interaction of pE19 with rec@ors on the dendm- salal surfaces of AH neunns. a-a”i”c -&pate. a” effec- tive antagonist of lW4 excitation, inhibits bath the toxic and IX-releasinn effects of t&S%. GABA blocks N&induced Ui release in a”dose-dqmde& &umer (100-1500 mg/kg SC) but does nat block TM toxicity. GABA inhibition of IMA ac- tion is antagonized by biaculline (1 r&kg SC) or mimicked by diazepfan (20 &kg SC). &I findings sqgest the possi- bility that AH neumns are involwd in gonadotrophin neum- regulation and that this systan nay be driven and inhibited respectively by amid acid excitatory (glutamergic or aspar- tergic) and inhibitory (GABAergic) transmitter inputs. Supported by Grants W-00259, NS-09156, W-14677 and Rs) Award MA-38894 (J.W.O.).