Dissimilarity Between the Responses to Adenosine Triphosphate or Its Related Compounds and Non‐adrenergic Inhibitory Nerve Stimulation in the Longitudinal Smooth Muscle of Pig Stomach

Abstract

1 Transmural electrical stimulation (TMS) of longitudinal smooth muscle strips taken from the cardiac portion of the pig stomach produced biphasic responses consisting of initial contractions followed by relaxations. The excitatory component was enhanced by neostigmine and abolished by atropine. After atropine treatment, TMS and nicotine or 1,1-dimethyl-4-phenyl-piperazinium, caused a relaxation or a relaxation followed by an after-contraction. All of these responses were abolished or reduced reversibly with tetrodotoxin and cocaine, while hexamethonium only abolished the response to ganglion-stimulating agents. 2 The relaxation caused by TMS reached a maximum amplitude at 5-10 Hz, and was entirely resistant to the effects of a-and P-adrenoceptor blocking agents, or a combination of them, and also to guanethidine. These results strongly suggested that the relaxation was elicited by stimulation of intramural non-adrenergic inhibitory neurones. 4 Stimulation of the intramural inhibitory neurones of the tissue consistently evoked an inhibitory junction potential, which showed a summation during repetitive stimulation. One the other hand, ATP elicited mainly a small depolarization of a few mV. 5 When the desensitization to ATP of the muscle was achieved in the presence of atropine and guanethidine, the relaxation induced by stimulation of the non-adrenergic inhibitory neurones could be evoked without any modification. 6 Dipyridamole neither potentiated the inhibitory responses due to stimulation of the intramural inhibitory neurones nor showed any consistent effect on the ATP-induced response. 7 From these results, it is unlikely that ATP, or any related compound, is the transmitter substance of the intramural inhibitory neurones in the longitudinal smooth muscle of the pig stomach.

Investigation of the interaction between cholinergic and nitrergic neurotransmission in the pig gastric fundus

“…This might be related to penetration problems of a-chymotrypsin into the tissue or to a third non-peptide transmitter. In longitudinal muscle strips of the pig gastric fundus, ATP seems not involved (Ohga & Taneike, 1977).…”

“…The pig gastric fundus is innervated by excitatory cholinergic and inhibitory NANC neurones (Ohga & Taneike, 1977;Miyazaki et al, 1991) and NO is a major contributor to NANC relaxation (Lefebvre et al, 1995). The aim of this study in the pig gastric fundus was to investigate the interaction between the cholinergic and nitrergic innervation.…”

Purinergic signalling in the gastrointestinal tract and related organs in health and disease

“…[11,23,229,316,344,429,430,521]), there is good evidence that ATP is involved in most species in concert with NO and, to a lesser extent, VIP [45,91,161,162,211,283,480,491,523,526,532,728,751]. Vagally induced NANC gastric relaxation of cat stomach is inhibited by P2 receptor desensitisation with α,β-methylene ATP (α,β-meATP), but it is likely that this is due to interference with ganglionic transmission in the vagal pathway, rather than neuromuscular blockade [176,177].…”

H1‐ AND H2‐RECEPTORS IN THE SMOOTH MUSCLE OF THE RUMINANT STOMACH

“…The preparation was allowed to equilibrate for 60 min, under a resting tension of 2 grams. Movements of the muscles were recorded isometrically with a mechano-electronic transducer on a pen recorder as described previously (Ohga & Taneike, 1977).…”