Ablation of NK1 receptors in rat nucleus tractus solitarii blocks baroreflexes.
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.
Riley
Jeffrey
J
Laboratory of Neurobiology, Department of Neurology, University of Iowa and Veterans Affairs Medical Center, Iowa City 52242, USA.
Lin
Li-Hsien
LH
Chianca
Deoclecio A
DA
Talman
William T
WT
D000818:Animals; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects; D000922:Immunotoxins / Q000494:pharmacology; D008297:Male; D008845:Microinjections; D064729:Neurokinin-1 Receptor Antagonists; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018040:Receptors, Neurokinin-1 / Q000096:biosynthesis; D054789:Ribosome Inactivating Proteins, Type 1; D000076985:Saporins; D017552:Solitary Nucleus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D013238:Stereotaxic Techniques; D013373:Substance P / Q000031:analogs & derivatives / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
D000922:Immunotoxins; D064729:Neurokinin-1 Receptor Antagonists; D018040:Receptors, Neurokinin-1; D054789:Ribosome Inactivating Proteins, Type 1; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; C468274:substance P-saporin; D009599:Nitroprusside; D010656:Phenylephrine; D013373:Substance P; D000076985:Saporins