Effect of intravenous calcitonin gene-related peptide antagonist on the laryngeal chemoreflex in piglets.
The laryngeal chemoreflex (LCR) is characterized by mixed apnea and cardiovascular instability and is elicited by applying water to the laryngeal mucosa of developing animals. The LCR may be fatal in very young animals, and the reflex has been postulated as a possible mechanism of sudden infant death syndrome. Several antagonists have been found to alter the severity of the LCR, but the primary neurotransmitters involved in mediating the reflex response are not yet well understood. This study investigates the effect, on the LCR, of the pharmacologic antagonism of calcitonin gene-related peptide (alphaCGRP), a neurochemical found in abundance in the mammalian laryngeal mucosa and its innervating system. The LCR was elicited in 10 mixed breed piglets, 17.7 days of age (12 to 22 days), before and during infusion of alphaCGRP 8-37, a pharmacologic inhibitor of alphaCGRP, and cardiorespiratory and laryngeal responses were compared. The duration of obstructive apnea decreased from 17.9 to 9. 8 seconds (P < 0.03) in the presence of alphaCGRP 8-37. Mean central apnea did not change for the group (P > 0.05), although it was completely inhibited in 2 animals. Cardiovascular changes were not significantly altered by the alphaCGRP inhibitor. alphaCGRP appears to play a regulatory role in the apneic response of the LCR, particularly its obstructive component, but not the cardiovascular response.