Changes in hypothalamic neuronal function related to hormonal induction of lordosis in behaving hamsters

The hypothalamus is known to be critical for the neuroendocrine control of sexual behavior, but the neural effects of gonadal hormones on behavior-related activity of hypothalamic neurons has received little investigation. The present study examined the effects on single hypothalamic neurons of lordosis-inducing estrogen and progesterone administration to behaving golden hamsters. The lordosis-inducing action of the hormones was associated with rapidly emerging, cumulative changes in the activity level and somatosensory responsiveness of neurons throughout the hypothalamus, as well as the appearance in most neurons of lordosis-correlated firing. This functional reconfiguration of hypothalamic neuronal properties resembled, in time course and other aspects, effects of estrogen and progesterone previously observed in hamster midbrain neurons. Although the firing rates of the hypothalamic neurons were typically low, the lordosis-related activity of these neurons was compatible with a role in the control of individual episodes of lordosis as well as a state-related tendency to exhibit the lordosis response.