Ovulation induced by LH-RH in rats made anovulatory by various experimental procedures

The injection of LH-RH induced ovulation in constant estrous rats (CEA), made anovulatory either by frontal hypothalamic deafferentation (FHD), or by exposure to continuous light (CL), or by neonatal androgenization (NA) with 0.500 mg testosterone propionate (NA500). Rats neonatally treated with 1.250 mg testosterone (NA1250) were almost unable to ovulate. 100% of FHD-CEA rats ovulated in response to 10 ng LH-RH, which is 1/3 of the lowest dose able to determine 100% of full ovulation in control proestrous rats. NA500-CEA rats, on the other hand, ovulated in response to doses comparable to those effective in the controls, whereas in CL-CEA rats the doses required for full ovulation were 2-3 times higher than in the controls. The results of these experiments demonstrate that the pituitary glands of CEA rats respond to the stimulation by the specific hypothalamic releasing factor. The pituitary response, however, appears enhanced in FHD-CEA rats and markedly depressed in CL-CEA animals.