Wild running and conditioned place aversion produced by microinjection of a GABA-A receptor antagonist into the inferior colliculus of the rat

Blockade of GABAergic transmission within the inferior colliculus (IC) induces wild running (WR). WR was shown to present behavioral similarities with aversive reactions elicited from brain periventricular structures. The aim of the present study was to check whether blockade of IC GABAergic transmission could induce aversion. Microinjections of semicarbazide, a GABA synthesizing blocker, or SR95531, a GABA-A receptor antagonist, into the IC were performed. The elicitation of aversive effects was assessed in the place conditioning paradigm. Bilateral microinjection of semicrbazide (6 μg/0.2 μl) or of SR95531 (1 ng and 3 ng in 0.2 μl) elicited WR and tonic seizures. Carbachol (2 μg in 0.2 μl), a cholinergic agonist, elicited myoclonic seizures but not WR. The vehicle did not elicit any of these behavioral reactions. Microinjection of the same doses of semicarbazide and SR95531 into the IC elicited place aversion shown by a decrease in the time spent in the drug paired compartment during the postconditioning test. Microinjection of carbachol also elicited place aversion whereas saline or bicuculline did not. These results suggest that the blockade of the tonic inhibition exerted by GABAergic terminals within the IC results in WR, Tonic seizures and aversive effect.