Gonadotrophin regulation in the lactating rat

Post-partum lactation in the rat is associated with follicular quiescence and an attenuation of gonadotrophin secretion. The present study demonstrates that the lactating rat responds to exogenous LH-releasing hormone (LH-RH) in a manner similar to dioestrous rats. Oestrogen priming increases the LH and FSH response to LH-RH to a smaller degree in ovariectomized, lactating, than in non-lactating, ovariectomized rats. Pituitary LH levels throughout lactation did not seem to be related LH-RH-induced LH release. A diminished post-castration rise in both LH and FSH, and a diminished positive feedback response to oestrogen administration were also observed and may indicate a disruption of gonadotrophin regulation at both the hypothalamic and the pituitary level.