Glycine receptor (gephyrin) immunoreactivity is present on cholinergic neurons in the dorsal vagal complex

We previously demonstrated that microinjection of exogenous glycine into th e nucleus tractus solitarii of anesthetized rats elicits responses that are qualitatively like those elicited by microinjection of acetylcholine at th e same site. The responses to glycine, like those to acetylcholine, are blo cked by administration of a muscarinic receptor antagonist and prolonged by administration of an acetylcholinesterase inhibitor. Furthermore, glycine leads to release of acetylcholine from the nucleus tractus solitarii and su rrounding dorsal vagal complex. An anatomical framework for interactions be tween glycinergic and cholinergic neurons was established by studies that i dentified glycine terminals and receptors in the dorsal vagal complex. The current study investigated the relationship between glycine receptors and n euronal elements that were immunoreactive for choline acetyltransferase in the dorsal vagal complex. Neurons that were immunoreactive for choline acet yltransferase were located in the dorsal motor nucleus of the vagus, hypogl ossal nucleus and nucleus ambiguus, and stained cells were also present in medial, intermediate, and ventrolateral subnuclei of the nucleus tractus so litarii. We found that glycine receptors, immunolabeled with an antibody to gephyrin, were present on cholinergic dendrites in the nucleus tractus sol itarii. Gephyrin immunoreactivity was also present on dendrites that did no t stain for choline acetyltransferase. These data further support the contribution of cholinergic neurons in media ting cardiovascular responses to glycine in the nucleus tractus solitarii. (C) 1999 IBRO. Published by Elsevier Science Ltd.