ABSTRACT
Several tissues of the genitourinary tract are innervated by the parasympathetic nervous system and, in most of these, activation of postjunctional muscarinic receptors causes smooth muscle contraction. In general, muscarinic receptors mediating contraction of detrusor muscle in rat, mouse, rabbit, and guinea-pig appear to be of the muscarinic receptor subtype. The ureteral smooth muscle functions to transport urine from the kidneys to the urinary bladder, by induction of peristalsis. Histochemical studies have demonstrated a rich cholinergic innervation of the intravesical ureter but not the proximal ureter. Muscarinic receptors may mediate contraction of the smooth muscle capsule although the subtype is undefined. In terms of the epididymis, the extent of cholinergic innervation varies according to species and location. The parasympathetic nervous system has been proposed to play an important role in tumescence and penile erection by contributing to relaxation of corpus cavernosum smooth muscle.
