Interaction between somatic and vagal afferent inputs in control of ventilation in 2-week-old rabbits.
Effects of saphenous nerve stimulation (SNS) on the Hering-Breuer expiratory-promoting reflex evoked by a positive tracheal pressure (PTR; 5 cmH2O) and on the diaphragmatic EMG (EMG(DI)), inspiratory (TI) and expiratory (TE) time, were studied in 16 urethane-anesthetized (1.2-1.6 g/kg, i.p.) spontaneously breathing 2-week-old rabbits. Positive P(TR) applied at the end of T(I) increased the subsequent TE to 255+/-29% (+/-S.E.; P < 0.0001) of control. SNS (1 sec train, 2 msec pulse, 6 Hz) applied at the onset of TE, shortened this TE by 42+/-3% (P < 0.0001). When SNS preceded positive PTR or positive PTR preceded SNS, the TE increased to 163+/-20 and 184+/-21% of control, respectively. These responses were not different, and smaller than that provoked by the PTR test alone (P < 0.003 and 0.05, respectively). The results show that in newborns somatic afferent stimulation attenuates the vagally mediated respiratory inhibition, whether immediately before or during the vagal stimulation.
Department of Physiology, McGill University, Montreal, Quebec, Canada. teresa@physio.mcgill.ca
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D000344:Afferent Pathways / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D003964:Diaphragm / Q000502:physiology; D004558:Electric Stimulation; D004576:Electromyography; D011175:Positive-Pressure Respiration; D011817:Rabbits; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology*