VAGAL-STIMULATION INDUCES EXPIRATORY LENGTHENING IN THE IN-VITRO NEONATE RAT

Respiration is modulated by lung mechanoreceptor feedback in vivo on a cycle-to-cycle basis. We replicated this modulation in vitro and test ed four stimulus protocols to identify which of these most closely rep licated in vivo responses to lung mechanoreceptor activation in mammal s. We activated pulmonary vagal afferent pathways by electrical stimul ation or by lung inflation, applied during expiration, which produces expiratory lengthening in vivo. In each modality, transient and tonic stimuli were applied. Stimuli were applied over a range of delays foll owing inspiratory termination. Tonic stimuli were maintained until sub sequent inspiratory onset. All stimulus modalities prolonged expiratio n (P < 0.05). These results indicate that the neural circuitry mediati ng pulmonary afferent modulation of expiratory duration is retained in vitro.