Mechanisms of immediate respiratory responses to chlorpromazine

¹ Department of Physiology, University of Colorado School of Medicine, Denver, Colorado

Following the intravenous injection of chlorpromazine (5 mg/kg) in dogs anesthetized with Pentothal-chloralose, respiratory inhibition occurs followed by stimulation. A fall in arterial blood pressure accompanies the respiratory responses. The evidence indicates that a reflex is involved with receptors for the inhibitory response and at least the major portion of the stimulation located in the thorax with afferent pathways in the vagus nerves. The inhibition and stimulation persist when the arterial blood pressure is compensated. The inhibition and most of the stimulation are eliminated by vagotomy. It is suggested that the respiratory responses are primarily due to the activation of chemical-sensitive receptors. A portion of the stimulation may be related to the fall in blood pressure.