Mating activates estrogen receptor-containing neurons in the female monkey brain

In contrast to some other species, the numbers of activated neurons in the brains of male and female macaques are high in both mated and unmated animals. Dual labeling with the 1D5 anti-estrogen receptor antibody and the c-fos polyclonal anti-c-fos antibody was used in 19 female cynomolgus monkeys to examine whether mating selectively increases the activation of neurons containing estrogen receptors (ER). Mated females, and social controls exposed to males without mating, were euthanized about 75 min after the start of the test, exactly 60 min after the first ejaculation (mated females, N = 7) and 75 min after the start of exposure to a male (social controls, N = 4). A second control group of unmated females (N = 8) remained in their individual cages until euthanasia. Neuronal nuclei containing Fos immunoreactivity (Fos-ir) alone, ER-immunoreactivity (ER-ir) alone, or both Fos-ir and ER-ir, were counted in 8 brain regions, but 2 of these regions contained too few ER-ir neurons to permit analysis. The proportion of ER-ir neurons colocalizing Fos-ir was significantly higher in the preoptic area (P = 0.027) and ventromedial hypothalamus (P = 0.04) of mated than of control females, suggesting the selective activation of ER-containing neurons by mating in these two brain regions known to be important in the control of female mating. The proportion of Fos-ir neurons not containing ER-ir was significantly lower in the cortical amygdala (P = 0.045) of mated than in control females, suggesting a selective deactivation of neurons not containing ER-ir.