Wild running and switch-off behavior elicited by electrical stimulation of the inferior colliculus: effect of anticonvulsant drugs.

The behavioral and motivational effects of electrical stimulation of the inferior colliculus (IC) were investigated. Electrical stimulations of either the dorsal part or ventral part of the IC both elicited wild running (WR). Nevertheless, the ventral part was found more sensitive than the dorsal part, as lower intensities were needed to elicit WR. Moreover, WR differed depending on the part of the IC stimulated. It stopped as soon as the stimulation was switched off when the ventral IC was stimulated, whereas it further persisted in a poststimulus WR when the dorsal IC was stimulated. This poststimulus WR was abolished by anticonvulsant drugs such as diazepam, phenytoin or sodium valproate. In an operant escape conditioning paradigm (switch-off test), only stimulation of the ventral IC readily sustained switch-off learning. Dorsal IC stimulations did not, possibly because of the poststimulus enduring effects of the stimulation, as evidenced by poststimulus WR. Indeed, the anticonvulsant drugs which abolished this poststimulus WR also permitted switch-off of dorsal IC stimulations. It is concluded that electrical stimulations of the IC (dorsal or ventral) elicit aversive effects and that WR elicited either by ventral or dorsal stimulation may represent the overt expression of these aversive effects.