Male rat sexual behavior induces changes in [3H]flunitrazepam binding

The effect of male rat sexual behavior on the binding of [3H]-flunitrazepam (FNP) in frontal cortex, hypothalamus and hippocampus was measured. The groups included were: (A) control (no sexual experience) handled males; (B) male rats sacrificed 24 h after their fifth mating experience; (C) males sacrificed 48 h after their fifth mating experience; (D) male rats sacrificed after 5 intromissions during the sixth mating experience; and (E) males sacrificed immediately after the ejaculation during the sixth mating experience. Relative to handled controls, significant decreases in maximal [3H]-FNP binding (Bmax) were observed in frontal cortex and hippocampus of animals sacrificed after 5 intromissions and in frontal cortex of rats sacrificed 24 h after the last mating experience. Relative to males sacrificed after 5 intromissions, males sacrificed immediately after ejaculation exhibited a rapid increase in Bmax in frontal cortex and hippocampus. No between-group differences in Kd for [3H]-FNP were noted, and sexual experience had no effect on the Bmax of [3H]-FNP in the hypothalamus.