Carotid Chemosensory Response to Caffeine in Developing Cats

Abstract

It has been suggested that the increase of ventilation with methylxanthines (caffeine, theophylline and aminophylline) is mainly due to a stimulation of respiratory centers in adult subjects (Sawynok, 1995). However, methylxanthines seem to act also on carotid chemoreceptors in newborns since caffeine failed to increase ventilation in chronically chemodenervated lambs (Blanchard et al, 1986). Also, aminophylline did not prevent the ventilatory depression elicited by hypoxia in chemodenervated piglets (Cattarossi et al, 1995). Indeed, aminophylline has been shown to enhance the ventilatory chemoreflex response to hyperoxia in newborn infants (Cattarossi, 1993). Despite the frequent use of caffeine in the treatment of neonatal apnea (Sawynok, 1995; Bairam et al, 1987), the magnitude of its effects on carotid chemosensory activity is still unclear. In the majority of studies, ventilation has been measured in order to evaluate the effects of methylxanthines on the peripheral chemoreceptors. The aims of the present study were tp determine the effects of caffeine on the carotid sinus nerve chemosensory activity (CSNA) and on its response to hypoxia in newborn and adult cats.