An in vivo method for testing putative GABA-like compounds

A technique is described that enables compounds with GABA-ergic properties to be rapidly identified in vivo. Electrical stimulation of the neostriatum in the conscious rat evoked a contralateral head-turn. Evidence is presented that this easily timed motor response involves, at least in part, GABA-ergic mechanisms in the globus pallidus. GABA drugs were injected through a cannula into the ipsilateral globus pallidus and their effects on head-turning observed. Known GABA agonists including muscimol slowed the head-turn, whereas the GABA antagonist picrotoxin facilitated it. A number of drugs such as baclofen, diazepam, and pentobarbitone which have been attributed with GABA-like properties behaved like GABA agonists in the head-turn model following either intrapallidal or intraperitoneal injection. Other drugs, e.g. tranquillizers, with no known GABA-like properties, did not effect the head-turn time.