Gender and estrous cycle differences in the response to the 5-HT1A agonist 8-OH-DPAT

The effects of the 5-HT1A agonist, 8-hydroxy-2-9(di-n-propylamino)tetralin (8-OH-DPAT) on eating behavior and on rectal temperature were examined in adult male rats and in diestrous, proestrous, and estrous female rats. The 5-HT1A agonist produced evidence of hyperphagia at some dose (0.125, 0.25, 0.5 and 1.0 mg/kg) in all groups examined. However, hyperphagia was most evident in diestrous females and least evident in proestrous and estrous rats. These findings are interpreted as an estrous cycle modulation of somatodendritic 5-HT1A autoreceptors. The hypothermic response to 8-OH-DPAT was present in all females and at all doses of 8-OH-DPAT (0.1, 0.25 and 0.5 mg/kg). These findings suggest that postsynaptic 5-HT1A sites involved in 8-OH-DPAT-induced hypothermia do not vary during the estrous cycle. However, males showed less hypothermia following 8-OH-DPAT than did females. The gender difference was evidenced primarily as a slower onset of hypothermia in males treated with the lower doses of the drug.