Effect of Neonatal Androgenization on the Testosterone Feedback Sensitivity in Adult Rats in Two Lighting Conditions

Abstract

Neonatally androgenized and intact adult male Wistar rats received daily, during 1 week, either testosterone propionate or sesame oil injections in periodic or constant light. Serum and pituitary gonadotropins and hypothalamic LHRH were measured. In periodic light, neonatal androgenization did not change the serum concentration or pituitary contents of gonadotropins, or the hypothalamic content of LHRH. Testosterone injections decreased serum concentration and pituitary content of gonadotropin of intact rats but failed to decrease the pituitary gonadotropin content of neonatally androgenized rats. In constant light, serum FSH was decreased in neonatally androgenized rats. Testosterone injections decreased both serum LH and FSH concentrations of intact rats but only serum LH of androgenized rats. Pituitary gonadotropin and hypothalamic LHRH contents remained unchanged. We conclude that neonatal androgenization renders the male rat hypothalamo-pituitary axis more resistant to changes of testosterone concentration in adulthood. Constant light did not sensitize the neonatally androgenized rats to testosterone, but on the contrary, testosterone injections were less effective in constant than in periodical light.

Orexin A and B levels in the hypothalamus of female rats: the effects of the estrous cycle and age

“…Food and drink were available ad libitum throughout the experimental period and the lights were on from 0800 to 2000 h. Vaginal smears were inspected daily for at least 2 weeks (2 weeks for the young rats and 5-6 weeks for the middle-aged animals) and inspected for cytology to establish regular/irregular cycling. Rats were decapitated in the afternoon at 1300 -1400 h. Trunk blood was collected and serum prepared as described previously (26). Brains were rapidly removed and hypothalamus and lateral hypothalamus were dissected from a brain slice between bregma co-ordinates of 1.0 -4.8 mm.…”