title: Cardiovascular responses to denervation of pulmocutaneous baroreceptors in toads.
abstract: Toad pulmocutaneous arterial baroreceptors are connected to afferent fibers carried in the recurrent laryngeal nerves (rLNs). Bilateral rLN denervation in conscious toads (Bufo marinus) caused 34 and 78% increases in heart rate (Fh) and systemic arterial blood pressure (Pa) within 10-15 min, respectively. The variance of Pa was significantly increased 2 days after denervation, but Pa and Fh were not. In additional chronic experiments, 5 of 17 baroreceptor-denervated toads died within the 2-wk recovery period. No deaths occurred in sham-operated toads. The mean Pa, Fh, and cardiac interval (Ic), the mean variance of Pa, Fh, and Ic, and Pa and Fh responses to stress, plasma composition, and the dry-to-wet weight ratio of skeletal muscle and lung were not statistically different in denervated and sham-operated toads. However, the sensitivity of Ic to changes in Pa, exposed by intra-arterial injections of phenylephrine and nitroprusside, was attenuated in denervated toads. Postmortem examination revealed occasional pulmonary lesions, the incidence of which appeared correlated with causes of pulmonary hypertension: baroreceptor denervation and phenylephrine injections. We conclude that pulmocutaneous arterial baroreflex is tonically active but is not essential for the long-term maintenance of Pa in conscious undisturbed toads.
authors.affiliation: Department of Physiology, University of Saskatchewan, Saskatoon, Canada.
authors.forename: B N
authors.initials: BN
authors.lastname: Van Vliet
authors.forename: N H
authors.initials: NH
authors.lastname: West
mesh_terms: D000818:Animals; D001794:Blood Pressure; D002024:Bufo marinus; D003714:Denervation; D006339:Heart Rate; D011311:Pressoreceptors / Q000502:physiology*; D012009:Recurrent Laryngeal Nerve / Q000502:physiology; D012018:Reflex / Q000502:physiology