Neurotensin-lmmunoreactive Neurons in the Rat Medial Preoptic Area are Oestrogen-Receptive

The identity of neurons influenced by oestrogen is critical for the understanding of ovarian steroid actions in the brain. The medial preoptic area (MPOA) contains one of the largest oestrogen-receptive cell populations in the rat brain and participates in several oestrogen-dependent functions, including the regulation of luteinizing hormone (LH) secretion and sexual behaviour. Using double immunostaining procedures with antibodies specific for the oestrogen receptor and neurotensin, a neuropeptide implicated in the regulation of LH secretion within this area, we found that approximately half of the neurotensin-immunoreactive neurons in the MPOA also displayed immunoreactivity for the oestrogen receptor. We estimate that oestrogen-receptive neurotensin neurons represent 5% to 12% of all oestrogen receptor-positive cells in the MPOA. Our results provide morphological evidence that neurotensin mediates oestrogen-dependent mechanisms within the brain and suggest that oestrogen may act through preoptic neurotensin neurons to aid in the generation of the LH surge.