The influence of neuronal 5‐hydroxytryptamine receptor antagonists on non‐cholinergic ganglionic transmission in the guinea‐pig enteric excitatory reflex

• Published in: British journal of pharmacology Vol. 107; no. 1; pp. 5 - 7
• Main Authors: Tonini, M., Coccini, T., Onori, L., Candura, S.M., Rizzi, C.A., Manzo, L.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.09.1992; Nature Publishing
• Subjects: 5‐HT receptor antagonists; 5‐hydroxytryptamine (5‐HT); Animals; ascending excitatory reflex; Benzamides - pharmacology; Benzimidazoles - pharmacology; Biological and medical sciences; Bridged Bicyclo Compounds - pharmacology; Bridged Bicyclo Compounds, Heterocyclic; Female; Fundamental and applied biological sciences. Psychology; Guinea Pigs; Indoles - pharmacology; Intestine, Small - drug effects; Intestine, Small - innervation; Intestine, Small - physiology; Intestine. Mesentery; Isolated small intestine; Male; Methiothepin - pharmacology; Muscle Contraction - drug effects; non‐cholinergic ganglionic transmission; Ondansetron - pharmacology; Serotonin Antagonists; Synaptic Transmission - drug effects; Synaptic Transmission - physiology; Tropisetron; Vertebrates: digestive system; Ganglionic transmission; Vertebrata; Mammalia; Guinea pig; Serotoninergic receptor; Serotonin; Digestive system; Animal; Gut; Rodentia; Ileum
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/j.1476-5381.1992.tb14455.x

A partitioned bath made it possible to separate the site of recording of the ascending excitatory reflex of the ileal circular muscle (oral compartment) from the site of reflex induction (caudal compartment), evoked by inflating an intraluminal balloon. In the caudal compartment, blockade of cholinergic ganglionic transmission by hexamethonium (100 μm) and hyoscine (0.3 μm) caused an approximately 65% reduction in the amplitude of reflex contractions, suggesting that the remaining response was mediated by non‐cholinergic transmission near the distension site. This non‐cholinergic component of ganglionic transmission was insensitive to the action of methiothepin (1 μm), ondansetron (1 μm), tropisetron (1.5 μm), DAU 6285 (1 μm) and renzapride (1 μm), agents that antagonize the action of 5‐hydroxytryptamine (5‐HT) at neural 5‐HT1‐like, 5‐HT3, 5‐HT4 and putative 5‐HT1P receptors. These findings suggest that the neural pathways subserving non‐cholinergic ganglionic transmission in the ascending excitatory reflex in the guinea‐pig ileum do not involve 5‐HT as neurotransmitter.