Immunocytochemical localization of progesterone receptors in galanin neurons in the guinea pig hypothalamus.

A double-label immunocytochemical technique was used to determine whether progesterone receptor-containing neurons in the female guinea-pig hypothalamus also contained galanin. Adult ovariectomized guinea-pigs were primed by estradiol to induce progesterone receptors and injected intracerebroventricularly with colchicine to visualize galanin-immunopositive neurons. A small proportion of progesterone receptor-containing perikarya in the medial preoptic area and the mediobasal hypothalamus were bound to be immunoreactive for galanin. The medial preoptic, periventricular and arcuate nuclei showed the greatest concentration of double-labelled cells. Galanin varicosities appeared in close proximity to neurons with progesterone receptor-containing nuclei. These results provide neuroanatomical evidence that a subset of hypothalamic galanin-immunoreactive neurons is directly regulated by progesterone.