EVIDENCE OF NONADRENERGIC, NONCHOLINERGIC CONTRACTION IN RAT URINARY-BLADDER BY 1,1-DIMETHYLPHENYLPIPERAZINIUM STIMULATION IN-VIVO

Nonadrenergic, noncholinergic (NANC) contraction has been demonstrated in animal urinary bladder. However, the exact nature of the NANC inne rvation is still unclear. 1,1-Dimethylphenylpiperazinium (DMPP), which generates action potentials in the cell body of the postganglionic ne uron and causes neurotransmitter release (both acetylcholine and norad renaline), was given intravenously (0.1-0.7 mg/kg) to 3-month-old fema le Wistar rats under anesthesia (n = 20). Intravesical pressure, heart rate and blood pressure of the rats were monitored on Gould polygraph . Monophasic dose-dependent contractile response was observed upon adm inistration of DMPP in 12 of 20 rats. After total adrenergic and choli nergic blockade with atropine, guanethidine, phentolamine and proprano lol, the contractile response was reduced, not completely, in the anim als. At the dose of 0.7 mg/kg, the contraction was reduced to about 48 % of the original response. The study provides in vivo evidence for NA NC contraction in the rat urinary bladder; moreover, the neurotransmit ter is released from the postganglionic neurons.