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(Hypertension. 2002;40:823.)
© 2002 American Heart Association, Inc.

Rapid Communications

Ablation of NK1 Receptors in Rat Nucleus Tractus Solitarii Blocks Baroreflexes

From the Laboratory of Neurobiology, Department of Neurology, University of Iowa and Veterans Affairs Medical Center (J.R., L.L., W.T.T.), Iowa City; and Department of Biological Sciences/NUPEB, Universidade Federal de Ouro Preto (D.A.C.), Ouro Preto, MG, Brazil.

Correspondence to William T. Talman, MD, Department of Neurology, University of Iowa, 200 Hawkins Dr, Iowa City, IA 52242. E-mail william-talman{at}uiowa.edu

The neuropeptide substance P (SP) is found in vagal afferent nerves within the nucleus tractus solitarii, where it is released on stimulation of arterial baroreflexes. The neurokinin-1 receptors at which SP may act have been identified in the nucleus tractus solitarii, but there remains uncertainty if the neurons at which SP acts are critical to baroreflex transmission. By using SP conjugated with the toxin saporin, which kills the neurons at which SP may act, we sought to test the hypothesis that neurons expressing the neurokinin-1 receptor are critical to baroreflex transmission in the nucleus tractus solitarii. One and 2 weeks after injection of the toxin into the rat nucleus tractus solitarii, immunoreactivity for the neurokinin-1 receptor was lost. When the toxin had been injected bilaterally, the baroreflex gain was significantly reduced. Therefore, neurons that express SP receptors play a critical role in mediating baroreflexes through the nucleus tractus solitarii of rat.

Key Words: baroreflex • blood pressure • receptors • neuropeptides

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