The hypothalamic levels of the endocannabinoid anandamide peak immediately before the onset of puberty in rats

Several data suggest that the endogenous cannabinoid system plays a role in neuroendocrine regulation in adult individuals, although the information on its involvement in peri-pubertal processes is scarce. In the present study, we have examined the ontogeny (from postnatal day [PND] 5 up to adulthood) of hypothalamic and anterior pituitary contents of anandamide (arachidonyl-ethanolamide, AEA). We observed that the content of AEA in the hypothalamus was low at PND5, PND15 and PND25, but it markedly increased (approximately 3-fold) immediately before the puberty (on the day of 1st proestrus), to return to intermediate values immediately after the vaginal opening (day of 2nd proestrus) and, eventually, adulthood. By contrast, no consistent differences were observed in AEA levels in the anterior pituitary. These results demonstrate the occurrence of a parallelism between the peri-pubertal events and a rise in the hypothalamic content of AEA immediately before the puberty, which might indicate that this endocannabinoid may be involved in the onset of puberty in rats.