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 innervation is still unclear. 1,1-Dimethylphenylpiperazinium (DMPP), which generates action potentials in the cell body of the postganglionic neuron and causes neurotransmitter release (both acetylcholine and noradrenaline), was given intravenously (0.1-0.7 mg/kg) to 3-month-old female 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 administration of DMPP in 12 of 20 rats. After total adrenergic and cholinergic blockade with atropine, guanethidine, phentolamine and propranolol, the contractile response was reduced, not completely, in the animals. 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 NANC contraction in the rat urinary bladder; moreover, the neurotransmitter is released from the postganglionic neurons.