The septum as origin of a lordosis-inhibiting influence in female rats: effect of neural transection.

The septum as the origin of a lordosis-inhibiting influence in female rats has been studied. Prior to testing, brain surgery was performed. Some rats were given a ventromedial cut (VMC) just above the anterior commissure, other rats, a posterior transverse cut (PC) or a dorsal horizontal cut (DC) just below the corpus callosum, and still other rats, a bilateral ventrolateral cut (VLC) in the ventrolateral septum and the bed nucleus of the stria terminalis (BST). Additionally, castrated females and those with a VLC sham operation served as castrated controls and sham-operated controls, respectively. All rats were given a daily dose of 0.2 micrograms of estradiol benzoate (EB) for three days and 0.5 mg of progesterone just prior to testing. The castrated controls evidenced no lordotic response. Lordotic activities also were very low in the surgically operated groups, with the exception of the VLC rats who demonstrated significantly high lordotic scores following the administration of 0.2 micrograms of EB. Two further testings, with the EB increased to 0.5 micrograms, were conducted, the interval between these tests being 2 weeks, and the VLC rats again demonstrated significantly higher lordotic activity than did the other rats. These results suggest that the septum exerts a lordosis-inhibiting influence, and that the ventrolateral outputs play a critical role in sending this inhibitory signal.