Differential role of serotonin and noradrenaline on anxiety reduction after ejaculation in the rat

As previously reported, a reduction in anxiety after ejaculation was observed. In a previous report it was demonstrated that the GABA-benzodiazepine system is involved in the mediation of this reduction in anxiety. The anxiety levels were measured using a defensive burying model. This work was performed to elucidate the serotonin and noradrenaline participation in the mediation of this phenomenon. Two experiments were made. In the first experiment the serotonergic neurotoxin 5,7-dihydroxytryptamine (5,7-DHT, 10 micrograms/10 microliters) was intracerebroventricularly injected. Five days after its administration the behavioral tests were performed. In the second experiment, the noradrenergic neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4, 50 mg/kg X 2) was IP administered. The neurochemical data reveal a drastic reduction in various brain areas respective monoamine levels after these treatments. The lesion produced by 5,7-DHT was able to reverse the reduction in anxiety in copulating males, but produced no changes in noncopulating animals. This finding supports the idea that the serotonergic system is involved in the reduction of anxiety observed after ejaculation. The results of the DSP4 experiment suggest that there is not a direct participation of the noradrenergic system in the anxiety reduction observed after ejaculation.