SEROTONIN(1A) RECEPTOR AGONISTS INDUCE FOS PROTEIN EXPRESSION IN THE LOCUS-COERULEUS OF THE CONSCIOUS RAT

The azapirones, which are partial agonists of the serotonin (5-HT)(1A) receptor, possess anxiolytic activity. These agents may act at the pr e- or postsynaptic 5-HT1A receptors, and involve the noradrenergic sys tem. To determine whether these drugs activate noradrenergic neurons v ia 5-HT1A receptors, we have evaluated the expression of the immediate early gene c-fos in the locus coeruleus. Tandospirone and ipsapirone each induced expression of Fos protein in the noradrenergic neurons of the locus coeruleus of conscious rats. This effect was reversed by pr etreatment with (+)-WAY100135, a specific 5-HT1A antagonist. These res ults clearly demonstrate that azapirones activate noradrenergic neuron s via 5-HT1A receptors.