Sexual experience increases nitric oxide synthase in the medial preoptic area of male rats.

Nitric oxide in the medial preoptic area (MPOA) is important for the expression and sensitization of male sexual behavior. In this article, the authors report that repeated sexual experience (mating for 2 hr on each of 3 days) increased levels of nitric oxide synthase (NOS) in the MPOA of male rats, regardless of whether they mated on the day they were given an overdose of sodium phenobarbital. This effect resulted from the previous experience and not acute mating, as NOS was not increased 2 hr after the first mating in previously naive males. Experience-induced increases in NOS in the MPOA may be one mechanism through which sexual experience facilitates sexual behavior in male rats.