NITRERGIC AND CHOLINERGIC INNERVATION OF THE RAT LOWER URINARY-TRACT AFTER PELVIC GANGLIONECTOMY

The possible coexistence of nitric oxide (NO) and acetylcholine in the rat major pelvic ganglion (MPG) was examined by double immunohistoche mistry using antisera raised against NO synthase (NOS) and choline ace tyltransferase (ChAT). The smooth muscle responses of the isolated bla dder and urethra were recorded after bilateral cryoganglionectomy of t he MPG, focusing on the possible development of denervation supersensi tivity. In the MPG, NOS immunoreactivity (ir) was seen in a large numb er of cell bodies, but it was not as abundant as ChAT-ir cell bodies. Double immunolabeling showed that all NOS-ir cell bodies also displaye d ChAT-ir. In ganglionectomized bladders, the electrical field stimula tion (EFS)-evoked contractile response was markedly reduced. When comp ared with control bladders, detrusor strips from ganglionectomized rat s were more sensitive to carbachol as revealed by a lower negative log arithm of the drug concentration eliciting 50% relaxation (6.5 +/- 0.0 4 vs. 5.9 +/- 0.07). In the urethra, the NO-mediated relaxant response to EFS was practically abolished by ganglionectomy, whereas no differ ence was found in sensitivity to 3-morpholinosydnonimine hydrochloride (SIN-1). SIN-1 produced an equal increase in tissue levels of guanosi ne 3',5'-cyclic monophosphate in urethral preparations from control an d ganglionectomized rats. The results suggest that the NOS-ir nerves t hat mediate inhibition of rat urethral smooth muscle tone originate fr om the MPG and contain ChAT. No denervation supersensitivity to nitrer gic stimulation was observed in the urethra after ganglionectomy.