Pretreatment with 5-HT(1A) receptor agonist flesinoxan attenuates Fos protein in rat hypothalamus

Abstract

The 5-HT(1A) receptor agonist flesinoxan has anxiolytic activity and concurrently enhances plasma corticosterone levels in rats. After a second injection of flesinoxan 24 h later, the corticosterone response disappears,but not the anxiolytic effects. Male rats received two injections with either flesinoxan or vehicle within 24 h. Flesinoxan challenge enhanced Fos immunoreactivity in the paraventricular nucleus of the hypothalamus, the central amygdala, and the dorsolateral part of the bed nucleus of the stria terminalis and plasma corticosterone levels in the vehicle-pretreated rats. Flesinoxan pretreatment resulted in an attenuated response of plasma corticosterone levels and Fos-positive neurons in the paraventricular nucleus of the hypothalamus, but not in the central amygdala and the bed nucleus after a flesinoxan challenge. The differential desensitization levels for both behaviour and neuroendocrine responses after flesinoxan treatment seem to correspond to different organization levels in the brain, like limbic system and hypothalamus.