Mechanisms for the tachypneic response to the thromboxane A2 mimetic U-46,619 in rabbits.
These experiments were designed to determine if intravenous infusion of the thromboxane A2 mimetic, U-46,619, would elicit tachypnea in the rabbit, and if so whether the afferent signal was generated by receptors innervated by myelinated or unmyelinated vagal nerve fibers. Intravenous infusion of U-46,619 (0.5 microgram/kg delivered over 10 s) increased breathing frequency (26%) and right ventricular blood pressure (59%) in the anesthetized rabbit (n = 10). Systemic arterial blood pressure, heart rate, and tidal volume were unaffected by the infusion of U-46,619. When myelinated fiber conduction in the vagus nerve was eliminated by bilaterally cooling the nerve to 6 degrees C, the increase in breathing frequency was only 5% above baseline levels. The tachypneic response to U-46,619 was totally eliminated when both myelinated and unmyelinated fiber conduction was abolished by cooling the vagi to 0 degree C. The increase in right ventricular blood pressure after U-46,619 infusion was unaffected by vagal cooling. Because most (> 80%) of the tachypneic response to U-46,619 was eliminated by blockade of myelinated vagal fiber conduction, we conclude that the tachypneic response to U-46,619 is mediated mostly by receptors innervated by myelinated vagal afferent fibers in the anesthetized rabbit.
Carrithers
J A
JA
Department of Physiology and Cell Biology, University of Kansas, Lawrence 66045.
Liu
F
F
Shirer
H W
HW
Orr
J A
JA
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D005246:Feedback; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology; D009413:Nerve Fibers, Myelinated / Q000187:drug effects / Q000502:physiology; D009431:Neural Conduction / Q000187:drug effects; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology*; D011817:Rabbits; D012119:Respiration / Q000187:drug effects*; D013928:Thromboxane A2 / Q000031:analogs & derivatives* / Q000494:pharmacology; D013990:Tidal Volume / Q000187:drug effects; D014132:Trachea / Q000187:drug effects / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D016278:Ventricular Function, Right / Q000187:drug effects / Q000502:physiology
D011450:Prostaglandin Endoperoxides, Synthetic; D014662:Vasoconstrictor Agents; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid