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Nicotinic transmission at functionally distinct synapses in descending reflex pathways of the rat colon
Author(s) -
Bian XC.,
Bornstein J. C.,
Bertrand P. P.
Publication year - 2003
Publication title -
neurogastroenterology and motility
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.489
H-Index - 105
eISSN - 1365-2982
pISSN - 1350-1925
DOI - 10.1046/j.1365-2982.2003.00393.x
Subject(s) - hexamethonium , neurotransmission , biology , inhibitory postsynaptic potential , stimulation , endocrinology , neurotransmitter , medicine , reflex , acetylcholine , neuroscience , nicotinic agonist , ganglionic blocker , receptor , central nervous system
We examined descending reflex pathways in the rat colon using intracellular recording techniques. Inhibitory junction potentials (IJPs) were recorded from circular smooth muscle when descending pathways were excited by combined mucosal compression and distension. IJPs were reduced to 71% of control when synaptic transmission was blocked in the oral stimulation chamber of a divided organ bath suggesting that two reflex pathways exist, the one involving descending sensory neurones and the other involving descending interneurones. Hexamethonium (200 μ mol L −1 ) in the recording chamber abolished reflexly evoked IJPs, while in the stimulation chamber, it was as effective as synaptic blockade. When hexamethonium was added to a chamber lying between the stimulation and recording chambers, it again sharply depressed IJPs to 27% of control; an extent similar to synaptic blockade. A P2 receptor antagonist did not reveal any purinergic neurotransmission. Either granisetron (5‐HT 3 receptor antagonist, 1 μ mol L −1 ) or SB204070 (5‐HT 4 receptor antagonist, 1 μ mol L −1 ) in the stimulation chamber significantly decreased IJPs; these decreases were not additive. We conclude that some sensory neurones and interneurones in rat colon have long anally projecting axons and that acetylcholine, acting via nicotinic receptors, is the primary neurotransmitter from sensory neurones, to inhibitory motor neurones and between interneurones.