PHARMACOLOGICAL SIMILARITY BETWEEN NITRIC-OXIDE AND THE NITRERGIC NEUROTRANSMITTER IN THE CANINE ILEOCOLONIC JUNCTION

In organ bath experiments, pyrogallol (30-100 mu M), and to a lesser e xtent L-cysteine (3 mu M), reduced nitric oxide (NO)-induced relaxatio n, but not the NO-mediated non-adrenergic non-cholinergic (NANC) relax ation elicited by field stimulation of the canine ileocolonic junction . In contrast, in a superfusion bioassay, pyrogallol (10-30 mu M) and L-cysteine (1 mu M) inhibited the biological activity of both the tran sferable nitrergic factor released from the canine ileocolonic junctio n in response to NANC nerve stimulation and NO, but not that of S-nitr oso-L-cysteine, S-nitrosoglutathione or S-nitroso-N-acetyl-D,L-penicil lamine. Based on the bioassay experiments, it is concluded that the ni trergic NANC neurotransmitter in the canine ileocolonic junction behav es pharmacologically like NO.