UNIT ACTIVITY IN THE DIENCEPHALON OF FEMALE RATS DURING THE OESTROUS CYCLE

Abstract

SUMMARY The spontaneous firing rate of 826 single cells, recorded from the anterior diencephalon of cyclic female rats, was analysed. In the thalamus no differences in the firing rates of populations of cells were observed during the 4 days of the oestrous cycle. However, during the afternoon of pro-oestrus the units recorded from the hypothalamus were faster firing than on the remaining 3 days, and were significantly more active (P < 0·05) than during the afternoon of metoestrus or dioestrus. The increase in unit activity at pro-oestrus was restricted to the ventral portion of the anterior hypothalamus. Since even sham recording sessions during pro-oestrus greatly reduced the ovulation rate, the increased unit activity is unlikely to be a sufficient cause of luteinizing hormone secretion, though it might be a necessary prerequisite or have some other sexually related significance.