Expression of sodium channel Nav1.6 in cholinergic myenteric neurons of guinea pig proximal colon

2006 
We wished to establish the functional identity of Nav1.6-expressing myenteric neurons of the guinea pig proximal colon by determining the extent of colocalization of Nav1.6 and selected neurochemical markers. Nav1.6-like immunoreactivity (-li) was primarily localized to the hillock and initial segments of myenteric neurons located near junctions with internodal fiber tracts. Immunoreactivity for Nav1.6 was co-localized with choline-acetyltransferase-li, representing 96% of Nav1.6-immunoreactive neurons; about 5% of these neurons showed co-localization with calretinin-li, but none with substance-P-li. Cholinergic neurons expressing Nav1.6 were amongst the smallest (somal area <300 μm2) of all cholinergic myenteric neurons observed. Only three of 234 Nav1.6-immunoreactive neurons exhibited nNOS-li, and none co-localized with calbindin-li. These data suggest that Nav1.6 is expressed in a small uniform population of cholinergic myenteric neurons that lie within the guinea pig proximal colon and that are likely to function as excitatory motor neurons.
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