Protein synthesis in the medial preoptic area is important for the mating-induced decrease in estrus duration in hamsters.

Abstract

Sexual receptivity in female hamsters potentially lasts for about 16 h. However, vaginal cervical stimulation (VCS) from a male during mating eventually reduces receptivity and can shorten the duration of behavioral estrus. The process by which this change in response to the male takes place is unknown. Recently, detection of the Fos protein has indicated that the medial preoptic area (POA) is one of the brain regions particularly responsive to VCS. Additionally, the POA may have an inhibitory effect on sexual receptivity. To determine if protein synthesis in the POA is required to initiate the VCS-induced decrease in estrus duration, a protein synthesis inhibitor (anisomycin, 0.50 microg) or a control substance (cholesterol) was applied bilaterally to the POA of steroid-primed ovariectomized female hamsters. Females were tested with a sexually active male at five time points following the initial test for sexual receptivity (hour 1, 2, 6, 12, and 24). Half of the females tested were allowed to receive VCS from a male, while half were fitted with vaginal masks to prevent penile intromission. Each group receiving VCS showed a significant decrease in lordosis duration evident between hour 2 and hour 6, except the group which received anisomycin in the POA. In this respect the POA anisomycin group was similar to animals which did not receive VCS. Hamsters with vaginal masks and the anisomycin/POA animals allowed to receive VCS exhibited their first decrease in lordosis duration between hour 6 and hour 12. These results indicate that protein synthesis is important for VCS-induced decrease in estrus duration in the POA.