p-Chloroamphetamine-induced rat ejaculation is not associated with the preoptic nucleus or medial nucleus amygdala

Aim:  In the rat, intraperitoneal injection of p-chloroamphetamine (PCA), which releases central 5-hydroxytryptamine (5-HT) from serotonergic nerve terminals, induces ejaculation, even in the absence of an estrus female or female-related smell information. It is well known that the medial preoptic nucleus (MPN) and the medial nucleus amygdala (MEA) play a major role in the control of male sexual behavior in mammals. We examined whether or not neuronal activity of the MPN and/or the MEA was associated with PCA-induced ejaculation. Methods:  Using c-Fos immunohistochemistry, we demonstrated a difference in the neural activities of the MPN and the MEA for ejaculation during copulation with an estrus female and ejaculation by PCA injection. Results:  Increased numbers of c-Fos-immunoreactive (c-Fos-IR) cells were found in the MPN and the MEA in the brains of the mating animals, whereas in the brains of the animals undergoing PCA-induced ejaculation there was no increase in the number of c-Fos-IR cells in the MPN and a small increase in the MEA. Conclusion:  Based on these results, ejaculation induced by PCA is not associated with the MPN. Moreover, the MEA is not the main act for this ejaculation. (Reprod Med Biol 2008; 7: 37-43).