Morphine and dynorphin(1–13) microinjected into the medial preoptic area and nucleus accumbens: effects on sexual behavior in male rats

The effects on sexual behavior of opiate receptor stimulation within A10 and A14 terminal areas were examined in the following experiments. Morphine (0.01–6 nmol) and dynorphin(1–13) (0.01–3 pmol) were microinjected into the medial preoptic area (MPOA). Morphine (10–100 pmol) and dynorphin (10–100 fmol) injected into the MPOA reduced both the latency to ejaculate and the number of intromissions triggering ejaculation. Morphine (6 nmol) produced a failure to resume copulating following the second ejaculation. Morphine (1–10 nmol) injected into the nucleus accumbens (ACC) shortened the latency to the first intromission and lengthened the second postejaculatory interval. Naloxone (3 mg/kg i.p.) reversed the effects of morphine on intromission latency and attenuated the lowering of ejaculatory threshold.