The autonomic innervation of the large intestine of the toad (Bufo marinus).
1. A study was made of the pelvic and the splanchnic nerve supplies to the toad large intestine. 2. Stimulation of pelvic nerve fibres in the 9th and 10th spinal nerves caused a series of contractions of the circular muscle, only the first of which was abolished by hyoscine. The entire response was blocked by d-tubocurarine. The response was not affected by capsaicin treatment. 3. Stimulation of the splanchnic nerves caused a rapid contraction followed by a prolonged relaxation. The relaxation was abolished by bretylium. The contraction was selectively antagonised by prolonged exposure to capsaicin. Splanchnic nerve stimulation also caused a slow, prolonged excitation that was abolished by bretylium. 4. Application of adrenaline caused relaxation of circularly cut strips of large intestinal wall, whereas substance P, acetylcholine, 5-hydroxytryptamine, somatostatin and galanin caused contraction. 5. The results suggest that stimulation of the pelvic nerves releases acetylcholine and a non-cholinergic co-transmitter from peripheral postganglionic neurons. Both the inhibitory response to splanchnic nerve stimulation and the subsequent slow excitation appear to be mediated by adrenergic nerves. The rapid capsaicin-sensitive excitation is likely to be due to release of substance P from antidromically activated afferent nerve fibres in the splanchnic outflow.
Department of Zoology, University of Melbourne, Parkville, Victoria, Australia.
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Murphy
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Campbell
D000818:Animals; D001341:Autonomic Nervous System / Q000187:drug effects*; D002024:Bufo marinus / Q000502:physiology*; D005260:Female; D066298:In Vitro Techniques; D007420:Intestine, Large / Q000294:innervation*; D008297:Male; D010388:Pelvis / Q000294:innervation; D013153:Splanchnic Nerves / Q000187:drug effects