The rat uterus generates and releases prostaglandins (PGs) of the series 2 as well as PGs of the series 1. The main purposes of the present study are to compare the effects of norepinephrine (NE) on the production and outputs of PGE1, PGE2 and PGF2 alpha by the uterus isolated from ovariectomized rats, treated or not with 17-beta-estradiol and to explore also, whether the effects of NE on PG synthesis are mediated through alpha, beta or both types of adrenoreceptors. Segments of control uterine horns obtained from ovariectomized rats generated and released into the incubating solution, equal amounts of PGE1, PGE2 and PGF2 alpha and propranolol (10(-6) M) or phentolamine (10(-6) M) failed to alter this basal production of PGs. Norepinephrine (3 X 10(-6) M) significantly depressed the outputs of PGE1 and PGF2 alpha but enhanced, also significantly, the release of PGE2. In the presence of the beta-adrenoreceptor blocker, propranolol, the reduction induced by NE on the output of PGE1 was not altered, but the stimulatory influence of NE on the release of PGE2 as well as the depression on the output of PGF2 alpha, were abolished. On the other hand the diminution evoked by NE on the release of PGF1 and PGF2 alpha as well as the increment induced on PGE2 output, were inhibited by the presence of phentolamine in the incubating solution. Uterine horns from ovariectomized rats treated with 17-beta-estradiol released into the incubating solution significantly more PGF2 alpha than PGE1 or PGE2. NE, either alone of in the presence of alpha 0 or beta-adrenoceptor blockers, did not modify this pattern of PG production. A possible mechanism(s) of action for NE on PG synthesis is discussed.