DMPP-induced relaxation of the guinea pig urinary bladder.

Abstract

KUWAHARA, M. DMPP-InducedRelaxation of the Guinea Pig Urinary Bladder. Tohoku J. exp. Med., 1980, 132 (3), 313-321 -Dimethylphenylpiperazinium (DMPP) caused a relaxation of a guinea pig urinary bladder in vitro when an intraluminal pressure of bladder had been increased by physo stigmine or histamine. The relaxing effect of DMPP was also observed in the contractions elicited by electrical stimulations.It was not blocked by hexa methonium, phenoxybenzamine, phentolamine, propranolol or tetrodotoxin. ATP and amines (such as glutamic acid, glycine, GABA, 5-HT and histamine) caused no relaxing effect on the physostigmine-induced contraction.The results indicate that the DMPP-induced relaxation appears to be a direct action of DMPP on the smooth muscle of the bladder and to differ from its adrenergic transmitter releasing or atropine-like action. -DMPP; relaxing effect; urinary bladder Dimethylphenylpiperazinium (DMPP) has been introduced as a ganglion stimulating agent and is generally used as a tool for studying effects mediated by the nicotinic receptor.In the urinary bladder, these agents are well known to cause a contraction (Taira 1972). In addition to its effect on the ganglion, other effects of DMPP, i.e. the release of adrenergic transmitter due to stimulation of nerve terminal (Lofferholz 1970;Holbach et al. 1977), and the atropine-like action MATERIALS AND METHODSAdult guinea pigs of either sex, weighing 300 to 400 g, were stunned by a blow on the head. Through a lower midline incision, the urinary bladder was exposed and both ureters were tied and cut. The urethra was cut at 2 mm distal from the bladder and the whole bladder was removed.A polyethylene cannula was inserted into the bladder through the urethra and the bladder was flushed out three times with 0.5 ml of modified Krebs solution.The solution had the following compositions (mM) ; NaCl 120.9, KCl 5.9, CaCl2 2.5, MgCl2 1.2, NaH2PO4 1.2, NaHC03 15.5, Glucose 11.1. The cannulated bladder was immersed in an organ bath (20 ml in capacity) filled with the same solution at 37°C, aerated with 95% oxygen and 5% carbon dioxide. The cannula was connected to a Received for publication, September 12, 1979. 313