Activation of luteinizing hormone-releasing hormone release advances the onset of female puberty

The juvenile-peripubertal transition period in the female rat is associated with an ovarian-independent afternoon increase in the amplitude of plasma luteinizing hormone (LH) pulses. To determine if the immature pituitary could be activated to cause precocious puberty juvenile female rats were subjected for 4 days to a microprocessor-driven pulsatile intravenous administration of LH-releasing hormone (LHRH) at a dose that produced a peripubertal pattern of LH release. To determine if the LHRH neurons themselves could be prematurely activated to induce such a pattern of plasma LH, and hence lead to precocious puberty, the neuroexcitatory amino acid analog N-methyl-DZ-aspartic acid (NMA) was similarly administered. The time of puberty (vaginal opening and first ovulation) was advanced by both the LHRH and NMA treatments, by 5 and 7 days, respectively. Ovarian weight and incidence of corpora lutea at first diestrus were similar in all animals regardless of treatment, but a juvenile body weight was retained by the animals that underwent precocious puberty. Therefore, just as the adenohypophysis can be driven by exogenous LHRH to initiate puberty, the LHRH neuronal system can be precociously activated by the episodic administration of an excitatory amino acid analog that is known to interact with specific brain receptors. It is likely, therefore, that sexual maturation is limited by factors that lie further upstream in the hypothalamo-pituitary axis (e.g., the neuronal circuits that impinge upon LHRH-producing neurons).