Development of a system for the non-invasive measurement of the time course of [C-11] nicotine

It is widely believed that the addictive effects of cigarette smoking derive largely from the rapid absorption of nicotine from the pulmonary system. The immediate effects of an inhaled bolus of nicotine on brain function are thought to provide potent reinforcement for smoking behavior and maintain dependence on tobacco. A greater understanding of the initial time course of nicotine in arterial blood may be useful in achieving a greater understanding of smoking behavior. An experimental system that non-invasively measures the initial time course of [C-11] nicotine in the body has been developed. This apparatus observes the inhalation of [C-11] nicotine injected into a cigarette and the arrival of [C-11] nicotine at four locations in the body: the throat, lungs, brain, and wrist. NaI(TI) scintillation crystals (3" /spl times/ 3") are used as coincident radiation detectors. Event pulses are processed to provide energy discrimination and processed with coincidence logic. Conservative calculations predict that 1 mCi of [C-11] nicotine will produce between 200 and 1500 coincidences per second in the four regions which allows the measurement of the arrival times with 0.5 s precision. The inhalation of the [C-11] nicotine is measured by a plastic scintillator detector placed around the cigarette. The observation of the decrease in activity in the cigarette provides an accurate identification of inhalation time.