Muscarinic receptor subtypes are differentially distributed across brain
stem respiratory nuclei.
Mallios, Vasiliki J., Ralph Lydic, and Helen A. Baghdoyan.
Department of Anesthesia, The Pennsylvania State University, College of
Medicine, Hershey, PA 17033, USA
APStracts 2:0009L, 1995.
Cholinergic mechanisms are known to play a key role in the regulation of
breathing, but the distribution of muscarinic receptor (mAChR) subtypes has
not been localized within brain stem respiratory nuclei. This study examined
the hypothesis that mAChR subtypes are heterogeneously distributed across
brain stem nuclei that control breathing. Using in vitro receptor
autoradiography, the results provide the first selective labeling and
quantitative mapping of M1, M2, and M3 mAChR subtypes in cat brain stem
regions known to regulate breathing. Among brain stem nuclei known to contain
respiratory-related neurons, the greatest amount of mAChR binding was
measured in the lateral and medial parabrachial nuclei and the lateral
nucleus of the solitary tract. Fewer mAChRs were localized in nuclei
comprising the ventral respiratory group (nucleus ambiguus, retrofacial
nucleus) and ventral medulla (retrotrapezoid nucleus and ventrolateral
medulla). The data provide an essential first step for future studies aiming
to specify the regulatory role of mAChR subtypes within brain stem
respiratory nuclei.
Received 23 September 1994; accepted in final form 12 January 1995.
APS Manuscript Number L281-4.
Article publication pending Am. J. Physiol. (Lung Cell. Mol. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 February 1995.