Effects of Antisense to the α2A-Adrenoceptors Administered into the Region of the Locus Ceruleus on Behaviors in Plus-Maze and Sexual Behavior Tests in Sham-Operated and Castrated Male Rats

摘要

Clinical and experimental findings have implicated brain α2-adrenoceptors in the regulation of many physiological functions, including sexual activity and stress-related behavior. However, which subtypes of the three α2-adrenoceptors that have now been cloned (α2A, α2B, and α2C) are involved in these controls have yet to be established. Here, we investigated the contribution of α2A-adrenoceptors of the locus ceruleus, the principal source of brain noradrenaline, to exploratory and sexual behaviors. Using administration of antisense oligodeoxynucleotide to inhibit the receptor expression, we found that reductions in brainstem α2A-adrenoceptor mRNA levels and α2-adrenoceptor densities induced by antisense treatment were not accompanied by any changes in the major characteristics of male sexual activity, such as mount latencies and numbers of mounts. However, in sexual behavior tests, antisense-treated male rats had decreased numbers of rearings and thus have higher percentages of behaviors positively correlated with sexual activity. Besides, antisense-treated animals had decreased anxiety in plus-maze tests. The data demonstrate that inhibition of α2A-adrenoceptor expression in the region of the locus ceruleus has an anxiolytic-like effect and facilitates male's attention to female in sexual behavior test.