Laryngeal reflex inhibition of breathing in piglets: influences of anemia and catecholamine depletion

Abstract
Laryngeal reflex inhibition of breathing was studied in 31 piglets of both sexes varying in age from 34 to 93 days. Continuing supramaximal electrical stimulation of 1 superior laryngeal nerve (SLN) was associated with spontaneous resumption of breathing within 1 min in animals more than 1 mo. of age. Respiratory rate and depth were reduced. Electrical stimulation of the SLN in those with severe- anemia (Hct[Hematocrit] = 8.0 .+-. 0.5%) caused extended apnea. An intermediate effect was observed in animals with normal Hct but given reserpine (2 mg/kg) 2 days prior to study. Apnea response was potentiated in these animals by reduction of the Hct from 22.8 .+-. 3.4% to 8.4 .+-. 1.1% by hemodilution. In normal piglets similar degrees of hemodilution had no discernible effects. An interrelationship between O2 availability, adrenergic activity and SLN-induced respiratory depression in young piglets is suggested.