Effect of GABA, GABA agonists and antagonists on gastric ulcer in rats

In the present investigation the effect of gamma-aminobutyric acid [GABA] on indomethacin [IM] [25 mg/kg orally] induced gastric ulcer in rats was studied. Results revealed that GABA at doses of 75 mg/kg [I.P.] and 150 mg/kg [I.P.] were devoid of significant effect on IM-induced ulceration, mean while higher doses of GABA 300 mg/kg [I.P.] and [450 mg/kg [I.P.] potentiated IM-ulceration. Regarding the effect of GABA antagonists, data proved that picrotoxin [2.5 mg/kg I.P] bicuculline [2.5 mg/kg I.P.] and pentylenetetrazole [PTZ] [25 mg/kg I.P.] blocked the aggravating effect of GABA on IM-induced gastric ulceration. It was noticed that GABA antagonists produced no significant changes on IM-ulceration. Also diazepam [0.5 mg/kg I.P.] and pentobarbital [5 mg/kg I.P.] potentiated the exacerbating effect of GABA on IM-induced gastric ulceration. At the same time both diazepam and pentobarbital were devoid of significant effect on IM-ulceration. In contrast GABA agonist muscimol [6 mg/kg orally] had cytoprotective effect against IM-induced gastric ulceration, while GABA agonist baclofen [6 mg/kg orally] showed no significant effect on IM- ulceration However, atropine [1 mg/kg I.P.] was protective against both IM-induced gastric ulceration and the GABA potentiating effect of IM -ulceration. The results suggested that GABA induced exacerbation of IM -ulceration might be due to the activation of peripheral muscarinic receptors in the stomach. This effect was mediated by stimulation of GABA[A] .-receptors and not GABA receptors in the stomach

Inhibition of renal electrolyte excretion by gabaergic pathways of the lateral hypothalamic area

Injection of gamma butyric acid (GABA) into the lateral hypothalamic area of unrestrained conscious rats caused a decrease in renal electrolyte excretion with an increase in urinary flow. When picrotoxin, a specific inhibito of gabaergic pathways, was administered, a significant increase in renal water and electrolyte excretion occured. The effect of simultaneous injection of pidrotoxin and GABA into the same site indicate that picrotoxin was less potent in reversing tyhe effect induceb by GABA than GABA was in reversing the effect of picrotoxin. We conclude that GABA acts directly on the neuronal mechanisms involved in the control of water and elecltrolyte excretion, perhaps by exerting a tonic inhibitory action on renal electrolyte excretion

Gabaergic fibers from substantia nigra para reticulata modulate escape bahavior induced by midbrain central gray stimulation

Eletrical stimulation or microinjection of GABA antagonists into the dorsal periaqueductal gray (DPAG) produces escape behavior. In order to determine whether the nigrocollicular gabaergic fibers exert some control over this behavior, rats bearing kainic acid lesion of the substantia nigra pars reticulata were submitted to microinjections of bicuculline or electrical stimulation of the DPAG at the escape threshold. Rats thus treated exhibited a significant decrease in the escape threshold while bicuculline increased the expression of flight behavior. These results suggest an inhibitory control of gabaergic fibers from the substantia nigra pars reticulata on aversive behavior induced by DPAG stimulation