Effects of C fiber blockade on cardiorespiratory responses to laryngeal stimulation in concious lambs.
The primary aim of the study was to explore cardiorespiratory reflexes originating from laryngeal C fiber endings in the neonatal period. Seventeen lambs were instrumented for recording glottal adductor and diaphragm EMG, heart rate, systemic arterial pressure and respiratory movements. C fiber blockade was induced in eight lambs by 30 mg/kg capsaicin, the remaining nine lambs serving as controls. Cardiorespiratory reflexes were induced in non-sedated lambs by flowing air, menthol or 13% CO2, or by injecting water or 50 microg capsaicin in the laryngeal inlet through an endoscope. Responses to all stimuli but capsaicin were similar between the two groups. While cardiorespiratory responses were induced by capsaicin in control lambs, the responses were significantly inhibited in lambs with C fiber blockade. We conclude that laryngeal C fiber endings are functional and responsible for laryngeal chemoreflexes in newborn lambs.
Roulier
Sébastien
S
Department of Pediatrics, University of Sherbrooke, PQ, Sherbrooke, Canada J1H5N4.
Arsenault
Julie
J
Reix
Philippe
P
Dorion
Dominique
D
Praud
Jean-Paul
JP
D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D000982:Antipruritics / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002211:Capsaicin / Q000494:pharmacology*; D002245:Carbon Dioxide / Q000494:pharmacology; D002320:Cardiovascular Physiological Phenomena / Q000187:drug effects; D003964:Diaphragm / Q000187:drug effects; D004562:Electrocardiography / Q000379:methods; D004576:Electromyography / Q000379:methods; D006041:Goats; D006339:Heart Rate / Q000187:drug effects; D007823:Laryngeal Nerves / Q000502:physiology*; D008610:Menthol / Q000494:pharmacology; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology*; D012018:Reflex / Q000187:drug effects; D012119:Respiration; D012129:Respiratory Function Tests; D020308:Songbirds / Q000502:physiology; D014851:Wakefulness / Q000502:physiology*; D014867:Water / Q000494:pharmacology
D000982:Antipruritics; D014867:Water; D002245:Carbon Dioxide; D008610:Menthol; D002211:Capsaicin