Midbrain lesions eliminate sexual receptivity but spare sexual motivation in female rats.

To measure sexual motivation we have used a preference test paradigm which involves testing a female with a sexually active male and a sexually inactive castrate male at the same time. On the assumption that a sexually motivated female will choose to spend more time with a partner who can provide her with stimulation appropriate to her motivational state, a female can be said to be sexually motivated to the extent that she spends more time with the active male than with the castrate. We find that bilateral destruction of the midbrain peripeduncular region eliminates the lordosis reflex in female rats, and abolishes sexual soliciting darting responses. Lesioned females treated with ovarian hormones continue, however, to show a strong preference for a sexually active male over a castrate. Thus, although peripeduncular destruction eliminates copulatory behavior, such destruction appears to spare hormone dependent systems for sexual motivation.