Chronic forced swim stress of rats increases frontal cortical 5-HT₂ receptors and the wet-dog shakes they mediate, but not frontal cortical β-adrenoceptors

We studied the effects of chronic forced swim stress on 5-HT₂ receptors and β-adrenoceptors in the rat frontal cortex. The number of 5-HT₂ receptors was increased immediately after the last chronic stress, but not after an acute stress. In vivo, the number of wet-dog shakes induced by a 5-HT₂ receptor agonist, (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), was increased 24 h after the last chronic stress. However, the concentrations of 5-HT and 5-hydroxyindole acetic acid (5-HIAA), measured by high pressure liquid chromatography (HPLC), were not altered by this stress. Binding sites for [³H]CGP-12177, i.e., β-adrenoceptor sites, were unchanged after both the acute and the chronic stress. These results suggest that, in the rat, the chronic forced swim stress increases the number of frontal cortical 5-HT₂ receptors and the number of wet-dog shakes mediated by these receptors, while the number of frontal cortical β-adrenoceptors is not increased by this treatment.