Involvement of 5-HT(1A) and 5-HT(2) receptors of the inferior colliculus in aversive states induced by exposure of rats to the elevated plus-maze test.

Abstract

Much evidence has shown that the inferior colliculus may be part of a brain system commanding defensive behavior. In the present work, evidence is presented for the serotonergic modulation of the neural substrate of aversive states elaborated in this structure. Rats implanted with a cannula in the inferior colliculus were tested on the elevated plus-maze. Microinjections of zimeldine, a 5-HT uptake blocker, produced increases in the percentage of open arm entries and time spent on the open arms. 8-OH-DPAT, a 5-HT(1A) agonist, and alpha-methyl-5-hydroxytryptamine, a highly selective 5-HT(2) agonist, injected directly into the inferior colliculus also produced clear anxiolytic-like effects in a dose-dependent manner. Based on these results we suggest that pharmacological interference with 5-HT mechanisms in the inferior colliculus may produce antiaversive effects.