The density of 5-hydroxytryptamine(2A) receptors in forebrain is increased at pro-oestrus in intact female rats

We have shown previously that in ovariectomised rats, oestradiol-17 beta, in its positive-feedback mode for luteinizing hormone (LH) release, induces a significant increase in the density of 5-hydroxytryptamine(2A) (5-HT2A) receptors in the forebrain. Here we investigated whether there are any changes in 5-HT,A receptor density in relation to the spontaneous surge of oestradiol-17 beta in female COB Wistar rats between dioestrus and pro-oestrus. Using [H-3]RP62203-binding and autoradiography, we found that 5-HT2A binding sites were significantly increased at 1630-1800 h on pro-oestrus compared with 0900-1130 h on dioestrus in frontal and cingulate cortex, olfactory tubercle and nucleus accumbens. The densities of 5-HT2A binding sites in male rats were similar to dioestrous female values in cortex, and to pro-oestrous female values in nucleus accumbens. The changes in the density of 5-HT2A binding sites in the forebrain of female rats may be relevant to oestrogen effects on mood and mental state. (C) 1997 Elsevier Science Ireland Ltd.