Background and reflex activity of guinea pig caudal mesenteric ganglion neurons |
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Authors: | O M Pasichnichenko V I Skok |
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Institution: | (1) Bogomolets Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine |
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Abstract: | The background activity of the guinea pig caudal mesenteric ganglion (CMG) neurons and their reflex reactions to colonic distension
were studied on isolated combined preparations including the CMG and a colon segment connected with the lumbar colonic nerves.
In the control, 62% of the neurons under study generated background activity, which consisted of irregular or regular “fast”
excitatory postsynaptic potentials (fEPSP) and action potentials (AP). In 27% of the CMG neurons called “pacemaker-like neurons”
(PLN), the background activity was represented by highly regular AP never observed in the CMG completely isolated from the
distal colon. Reflex responses evoked by colonic distension were recorded from 76% of the units studied. The distension evoked
fEPSP and AP in “silent” neurons and increased the background activity. Both the background activity and reflex responses
were shown to be due to nicotinic cholinergic transmission. In some neurons, reflex responses (regular AP) were generated
as superimposed on a slow depolarization; the latter was insensitive to nicotinic antagonists and either sensitive or insensitive
to muscarinic antagonists. It has been concluded that CMG neurons receive nicotinic, muscarinic, and, probably, peptidergic
afferent inputs from the distal colon. Although there are no true pacemaker neurons in CMG, some neurons generate pacemaker-like
activity of a synaptic origin. |
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