The role of substance P in the human urinary bladder.

Detrusor muscle from human bladder contracted to field stimulation after atropine. It also responded to exogenous substance P by an atropine-insensitive mechanism. We tested whether substance P might mediate noncholinergic excitation. Tachyphylaxis to substance P did not effect noncholinergic responses to field stimulation. A substance P antagonist was ineffective in blocking responses to field stimulation or to exogenous substance P. Capsaicin had only nonspecific depressant effects on field stimulated contraction in high (10(-4) M) concentrations. These data do not support the hypothesis that substance P is the mediator of noncholinergic, field stimulated contractions of human detrusor muscle.