The Regulation of Neuropeptide Expression in Rat Anterior Pituitary following Chronic Manipulation of Estrogen Status: A Comparison between Substance P, Neuropeptide Y, Neurotensin, and Vasoactive Intestinal Peptide

The neuropeptides substance P, neuropeptide Y, neurotensin, and vasoactive intestinal peptide are present in normal rat anterior pituitary gland and hypothalamus and can influence the secretion of classical pituitary hormones. We investigated the effects of estrogen manipulation on pituitary and hypothalamic expression of these four peptides by specific RIAs and cDNA probe analysis. Surgical ovariectomy produced a significant rise in the pituitary content of substance P immunoreactivity (IR) (130.2 ± 4.8 fmol/gland us. control 29.1 ± 2.2, P < 0.001), neuropeptide Y IR (34.9 ± 3.9 vs. 19.6 ± 2.0, P < 0.05) and neurotensin IR (85.1 ± 8.2 vs. 62.4 ± 7.2, P < 0.05), while vasoactive intestinal peptide IR showed a fall (201.2 ± 18.8 us. 285.4 ± 25.9, P < 0.05). These patterns were reversed with estrogen replacement or high dose estrogen treatment. Changes in peptide content were accompanied by parallel changes in the mRNA for each peptide. Treatment with an antiestrogen (tamoxifen) resulted in no change in sub...