Influence of nicotine in cigarette smoke on acute ventilatory responses in awake dogs

To determine whether the acute ventilatory responses to inhaled cigarette smoke are affected by a difference in nicotine level, control cigarettes (low-nicotine research cigarettes) were laced with nicotine to generate an increase of 330% (mean) in nicotine content with little or no change in the levels of other smoke constituents. Acute ventilatory responses to both control and nicotine-laced cigarettes were determined and compared in six awake chronic dogs. Spontaneous inhalation of nicotine-laced cigarette smoke (10% concn, 750 ml vol) via a tracheostomy tube caused distinct and consistent changes in breathing pattern on the first or second breath of inhaled smoke: an apnea in three dogs, an augmented inspiration in two dogs, and rapid shallow breathing in one dog. No significant change in breathing pattern was found immediately following inhalation of control cigarette smoke. Both types of cigarettes caused a delayed hyperpnea. However, the increase in minute ventilation induced by nicotine-laced cigarettes (from a base line of 2.8 to a peak of 25.7 l/min) was significantly greater than that by control cigarettes (from 2.9 to 5.5 l/min). Results of this study suggest that nicotine is responsible for the elicitation of both the immediate and delayed ventilatory responses to inhaled cigarette smoke generated under our experimental conditions.