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Targets of myenteric interneurons in the guinea‐pig small intestine
Author(s) -
Neal K. B.,
Bornstein J. C.
Publication year - 2008
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 - 10.1111/j.1365-2982.2007.01052.x
Subject(s) - calretinin , interneuron , enteric nervous system , myenteric plexus , biology , vasoactive intestinal peptide , neuroscience , cholinergic , inhibitory postsynaptic potential , motor neuron , anatomy , neuropeptide , spinal cord , receptor , immunohistochemistry , biochemistry , immunology
Polarized outputs of myenteric interneurons in guinea‐pig small intestine have been well studied. However, the variety of motility patterns exhibited suggests that some interneuron targets remain unknown. We used antisera selected to distinguish interneuron varicosities and known myenteric neuron types to investigate outputs of three interneuron classes in guinea‐pig jejunum; two classes of descending interneurons immunoreactive (IR) for somatostatin (SOM) or nitric oxide synthase (NOS)/vasoactive intestinal peptide (VIP), and one class of ascending interneurons [calretinin/enkephalin (ENK)‐IR]. Varicosities apposed to immunohistochemically identified cell bodies were quantified by confocal microscopy. Intrinsic sensory neurons (calbindin‐IR) were apposed by few varicosities. Cholinergic secretomotor neurons (neuropeptide Y‐IR) were apposed by many SOM‐IR varicosities. Longitudinal muscle excitatory motor neurons (calretinin‐IR) were apposed by some VIP‐ and ENK‐IR varicosities, but few SOM‐IR varicosities. Ascending interneurons (calretinin‐IR) were apposed by many varicosities of all types. NOS‐IR interneurons and inhibitory motor neurons were apposed by numerous VIP‐IR and SOM‐IR varicosities. NOS‐IR short inhibitory motor neurons were apposed by significantly fewer ENK‐IR varicosities than other NOS‐IR neurons. Based on the specific chemical coding of ascending (ENK) and descending (SOM) interneurons, we conclude that cholinergic secretomotor neurons and short inhibitory neurons are located in descending reflex pathways, while ascending interneurons and NOS‐IR descending interneurons are focal points at which ascending and descending pathways converge.