NICOTINE EXCITES CARDIAC VAGAL NEURONS VIA 3 SITES OF ACTION

1. Nicotine is involved in many cardio-respiratory diseases, including hypertension and sudden infant death syndrome (SIDS), which is the mo st common cause of death in infants between 1 month and 1 year of age, While the aetiology of SIDS remains largely unknown, recent clinical studies suggest maternal cigarette smoking is a major risk factor in S IDS and an abnormality of cardio-respiratory control, particularly a c entrally mediated slowing of the heart that precedes or accompanies ap noea, is involved. 2. Because the sites, mechanisms of action and dive rse receptor types of nicotine within the central nervous system are c ontroversial and poorly understood, in the present study we examined t he effects of nicotine on specific brainstem neurons that control hear t rate, Cardiac vagal neurons were identified in an in vitro slice pre paration using a retrograde fluorescent tracer and were studied using both whole-cell and perforated patch-clamp electrophysiological techni ques. 3. We have found there are different pre- and post-synaptic nico tinic receptors that have dramatic effects on glutamatergic neurotrans mission as well as directly activating vagal cardioinhibitory neurons.