Role of vagal afferents in the reflex effects of capsaicin and lobeline in monkeys.
Reflex effects of pulmonary C-fiber receptor stimulation by right atrial injections of capsaicin and lobeline were investigated in conscious monkeys (n=17). Capsaicin injection (15.0+/-1.4 microg/kg) produced apnea mostly (n=15, latency-1.7+/-0.2 s) and bradycardia, which were abolished by vagotomy (n=4). Lobeline administration (142+/-6 microg/kg) produced either apnea (n=7, latency -2.0+/-0.3 s) or excitation of breathing (n=8, latency -3.5+/-0.3 s) and no change in heart rate. After vagotomy (n=4), the apneic response was abolished, but the respiratory excitation persisted. Neither capsaicin nor lobeline produced cough. In the anesthetized monkey also (n=7), lobeline injection (50-150 microg/kg) did not produce any cardiovascular response. However, it produced excitation of breathing, which persisted after vagotomy but was abolished by carotid sinus denervation. It is concluded that in the non-human primate, it is capsaicin that produces reflexes typical of pulmonary C-fiber receptor stimulation, and cough is not a part of this reflex.
Department of Physiology, V.P. Chest Institute, University of Delhi, PO Box 2101, Delhi-110007, India.
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D000344:Afferent Pathways / Q000502:physiology; D000758:Anesthesia; D000818:Animals; D001049:Apnea / Q000209:etiology / Q000503:physiopathology; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D001919:Bradycardia / Q000209:etiology / Q000503:physiopathology; D002211:Capsaicin / Q000494:pharmacology*; D002346:Carotid Sinus / Q000294:innervation; D003371:Cough / Q000209:etiology / Q000503:physiopathology; D003714:Denervation; D006801:Humans; D008120:Lobeline / Q000494:pharmacology*; D008253:Macaca mulatta; D008297:Male; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology; D012018:Reflex / Q000187:drug effects* / Q000502:physiology*; D015656:Respiratory Mechanics / Q000187:drug effects* / Q000502:physiology*; D013045:Species Specificity; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology*
D008120:Lobeline; D002211:Capsaicin