Effects of norepinephrine on cyclic nucleotide levels in the ductus deferens of the rat.

The effect of 1-norepinephrine on cyclic nucleotide levels was studied in rat ductus deferens. Norepinephrine (0.01-0.3 mM) increased cyclic AMP and cyclic GMP levels in a concentration-dependent manner. Cyclic GMP was increased by about two-fold and cyclic AMP by 30%-40% by 0.1 mM norepinephrine after 3 min. Phenylephrine (0.1 mM) increased cyclic GMP levels about twofold without affecting cyclic AMP. Cyclic GMP was maximally increased by norepinephrine or phenylephrine after 3-10 min, but was not significantly changed after 20 sec, when contraction was fully developed. Atropine did not affect the norepinephrine-induced changes in cyclic nucleotide levels; phentolamine blocked the effect of norepinephrine on cyclic GMP, and propanolol blocked that on cyclic AMP. These findings indicate that in the ductus deferens alpha-adrenergic receptors are involved in the effect of catecholamines on cyclic GMP, and beta-adrenergic receptors are involved in the effect on cyclic AMP levels. The presence of Ca-2+ was required for the effect of norepinephrine on cyclic GMP, but not on cyclic AMP.