Somatosensory determinants of lordosis in female rats: Behavioral definition of the estrogen effect.

By coating the ventral surface of 16 Sprague-Dawley male rats with a dye, regions of contact between males and females ( n = 76) during male mounting were recorded precisely on the female's hair and skin. Film analyses showed that the male's paws and pelvic thrusting stimulated the female's skin with dominant frequencies between 10 and 20/sec. Somatosensory stimuli were then applied to the female skin locations contacted by the male. Deflection of hair on the flanks or perineum alone did not cause lordosis. Light stimulation simultaneously on flanks and perineum caused lordosis only in some females given high estrogen dosages supplemented by progesterone. When flank stimuli were followed by pressure on the rump, tailbase, and perineum, lordosis was triggered reliably in hormone-treated females. In this case, the estrogen-dependence of the reflex was shown, and progesterone synergized with the estrogen effect. Among lordosis components, rump and head elevations in response to pressure stimuli on the rump, tailbase, and perineum appear to be hormone-sensitive. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)