Site-specific inhibition of receptivity by intracranial anisomycin in hamsters

The ventromedial nucleus of the hypothalamus (VMH) has been implicated in the mediation of the hormonal control of female rodent sexual behavior. However, in hamsters, progesterone (P) has been found to have effects on sexual receptivity in other diencephalic and mesencephalic sites as well. Progesterone is thought to exert its behavioral effects by altering protein synthesis in CNS target neurons. We tested the effects of 30 gauge implants of the protein synthesis inhibitor anisomycin in the preoptic area (POA), VMH, and ventral mesencephalon (VMES) 30 minutes before 500 micrograms P SC, on the facilitation of lordosis in ovariectomized estrogen-primed female hamsters. The same animals were tested one week later with estrogen and progesterone treatment but without anisomycin. Anisomycin reduced sexual receptivity (lordosis) when placed in the VMH or VMES, but not when delivered to the POA. The results confirm the importance of the VMH in the mediation of progesterone facilitation of female sexual behavior, but also provide evidence that ventral midbrain structures may play a role in female sexual receptivity in hamsters. These two structures may be important for different aspects of lordosis. Progesterone effects in both sites appear to be protein synthesis dependent.