Increase in hypothalamic nicotinic acetylcholine receptors in prepuberal female rats administered estrogen

In previous studies, it has been reported that the administration of estrogen to prepuberal female rats produces precocious surges in the serum concentrations of luteinizing hormone (LH) and prolactin and the number of synaptic contacts in the arcuate nucleus. In the study reported here, we tested the hypothesis that the concentration of hypothalamic nicotinic acetylcholine receptors is the synaptic event initiating the precocious hormonal surges. A single injection of estrogen was administered to prepuberal female rats on day 25 and the serum concentrations of LH and prolactin and the concentration of the binding sites for alpha-bungarotoxin (BuTX), a putative nicotinic acetylcholine receptor ligand, were measured on day 27. The concentration of hypothalamic BuTX binding sites was increased by the estrogen treatment, but we found no evidence that this increase in receptors precedes or initiates the serum hormonal surges.