The Effect of Quipazine, A Serotonin Receptor Agonist, on Serum Corticosterone Concentration in Rats

Quipazine, a serotonin receptor agonist, increased serum corticosterone within 30 min after its i.p. injection (at 10 mg/kg) into rats; the effect persisted at 1 and 2 hrs, but not at 4 hrs. Elevation of serum corticosterone did not occur with a 1.25 mg/kg dose of quipazine but was dose-related over a 2.5-20 mg/kg dose range. The effect of quipazine was completely prevented by methergoline, a serotonin receptor antagonist. The effect of quipazine was present in rats pretreated with 5,7-dihydroxytryptamine to destroy serotonin nerves and was not enhanced (as was the effect of L-5-hydroxytryptophan) by fluoxetine pretreatment. These data are compatible with the idea that quipazine increases serum corticosterone as a consequence of direct stimulation of serotonin receptors in brain.