CONVERGENCE OF SUBSTANCE-P AND ESTROGEN-RECEPTOR IMMUNOREACTIVITY IN THE MIDBRAIN CENTRAL GRAY OF FEMALE GUINEA-PIGS

Substance P (SP) and estrogen receptor immunoreactivity overlap in the midbrain central gray (MCG) of female guinea pigs. Estrogen-receptor- containing cells are found throughout the rostrocaudal extent of the M CG. Moderately dense SP immunostaining is also found in this region. S P-immunoreactive punctate structures suggestive of boutons were found in close association with the processes of some estrogen-receptor-immu noreactive neurons. These associations were observed primarily in the lateral and ventrolateral MCG at the midcollicular and caudal levels. This finding suggests an anatomical substrate for interactions between SP and estradiol-sensitive neurons in the midbrain. Such interactions may underlie the effects of SP on female sexual behavior.