Nodose ganglionectomy selectively reduces muscarinic cholinergic and delta opioid binding sites in the dorsal vagal complex of the cat
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The dorsal vagal complex of the medulla oblongata, comprising the nucleus tractus solitarii, the area postrema and the dorsal motor nucleus of the vagus nerve, is an important brainstem regulatory center for the autonomic nervous system. The major afferent input from abdominal and thoracic viscera to this region is via vagal sensory neurons which have their cell bodies in the nodose ganglion. Autoradiography has been used to study the effects of unilateral nodose ganglionectomy on receptor binding sites in this region of the brain for the neurotransmitters acetylcholine, norepinephrine, and opioids. Nodose ganglionectomy had no discernible effect on alpha 2 noradrenergic ([3H]p-aminoclonidine) or mu opioid [( 3H]Tyr-D-Ala-Gly-(NMePhe)-Gly-ol) binding sites. However, ganglionectomy did produce a 25% decrease in [3H]quinuclidinyl benzilate (muscarinic cholinergic) binding in the subnucleus gelatinosus of the solitary nucleus, and a marked decrease in [3H][D-Pen5]enkephalin (delta opioid) binding in the dorsomedial subnucleus of the nucleus tractus solitarii, ipsilateral to the lesion. These data suggest that muscarinic cholinergic and delta opioid receptors may be present on terminals of vagal afferent neurons that project to these specific brainstem regions. Since these vagal afferent neurons are known to arise, at least in part, from the gastrointestinal tract, it is possible that cholinergic and/or opioid receptors modulate specific autonomic functions associated with gastric sensory information such as satiety or nausea and emesis.
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