Non-Cholinergic, Non-Adrenergic Nerve Mediated Relaxation of Trigone, Bladder Neck and Urethral Smooth Muscle in Vitro

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Abstract
Human trigone and porcine urethral, bladder neck and trigone smooth muscle were exposed to transmural electric field stimulation in vitro. The responses were composed of different combinations of a relaxation phase and a contraction phase. A few strips exhibited contractions only and a few strips relaxation only. The individual strip retained the behavior throughout the experiment. No systematic difference in the responses was found in strips from the different regions. The configuration of the response was slightly shifted in favor of contraction by .beta.-adrenergic blockade with propanolol and prostaglandin synthesis inhibition with Ketoprofen. After .alpha.-adrenergic blockade with phentolamine and cholinergic blockade with atropine, the reverse effect was seen with augmentation of the relaxation and reduction of the contraction. The relaxation phase was completely abolished by nerve poisoning with tetrodotoxin, but was still observed with all other antagonists present, and was therefore nerve-mediated through noncholinergic, nonadrenergic and nonprostaglandin transmitter or modulator systems.