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This Article Full Text Full Text (PDF) All Versions of this Article: 294/3/R720    most recent 00630.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Herman, M. A. Articles by Gillis, R. A. Search for Related Content PubMed PubMed Citation Articles by Herman, M. A. Articles by Gillis, R. A.

APPETITE, OBESITY, DIGESTION, AND METABOLISM

Characterization of noradrenergic transmission at the dorsal motor nucleus of the vagus involved in reflex control of fundus tone

¹Interdisciplinary Program in Neuroscience, ²Departments of Pharmacology and ³Medicine, Georgetown University Medical Center, Washington, District of Columbia

Submitted 31 August 2007 ; accepted in final form 9 January 2008

Quantitative analysis of innervation to dorsal motor nucleus of the vagus (DMV) fundus-projecting neurons indicates that 17% of input neurons are noradrenergic. To determine whether this small percentage of neurons innervating DMV output to the stomach is physiologically relevant, we evaluated the role of norepinephrine at the DMV in mediating a vagovagal reflex controlling the fundus. A strain gauge was sutured onto the fundus of isoflurane-anesthetized rats to monitor changes in tone evoked by esophageal distension (ED). ED produced a decrease in fundus tone of 0.31 ± 0.02 g (P < 0.05), which could be reproduced after a 30-min interval between distensions. Bilateral cervical vagotomy and/or pretreatment with intravenous atropine methylbromide prevented the reflex-induced fundus relaxation. In contrast, intravenous N^G-nitro-L-arginine methyl ester had no effect. Bilateral microinjection of ₂-adrenoreceptor antagonists (yohimbine and RS-79948) into the DMV also prevented the response. Before microinjection of ₂-adrenoreceptor antagonists, ED decreased fundus tone by 0.33 ± 0.05 g (P < 0.05). After antagonist microinjection, ED decreased fundus tone by only 0.05 ± 0.06 g (P > 0.05). Bilateral microinjection of prazosin into the DMV had no effect on the response. Microinjection of norepinephrine into the DMV mimicked the effect of ED and was also prevented by prior microinjection of an ₂-adrenoreceptor antagonist. Our results indicate that noradrenergic innervation of DMV fundus-projecting neurons is physiologically important and suggest that norepinephrine released at the DMV acts on ₂-adrenoreceptors to inhibit activity in a cholinergic-cholinergic excitatory pathway to the fundus.

gastric tone; norepinephrine; rat

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				M. A. Herman, M. T. Cruz, N. Sahibzada, J. Verbalis, and R. A. Gillis GABA signaling in the nucleus tractus solitarius sets the level of activity in dorsal motor nucleus of the vagus cholinergic neurons in the vagovagal circuit Am J Physiol Gastrointest Liver Physiol, January 1, 2009; 296(1): G101 - G111. [Abstract] [Full Text] [PDF]