DIFFERENTIAL SELECTIVITY OF CARDIAC NEURONS IN SEPARATE INTRATHORACICAUTONOMIC GANGLIA

Analyses of activity generated by neurons in middle cervical or stella te ganglia versus intrinsic cardiac ganglia were performed to determin e how neurons in different intrathoracic ganglia, which are involved i n cardiac regulation, interact. Discharges of 19% of intrathoracic ext racardiac neurons and 32% of intrinsic cardiac neurons were related to cardiodynamics. Epicardial touch increased the activity generated by similar to 80% of intrinsic cardiac neurons and similar to 60% of extr acardiac neurons. Both populations responded similarly to epicardial c hemical stimuli. Activity generated by neurons in intrinsic cardiac ga nglia demonstrated no consistent short-term relationships to neurons i n extracardiac ganglia. Myocardial ischemia influenced extracardiac an d intrinsic cardiac neurons similarly. Carotid artery baroreceptors in fluenced neurons in ipsilateral extracardiac ganglia. After decentrali zation from the central nervous system, intrinsic cardiac neurons rece ived afferent inputs primarily from cardiac chemosensitive neurites, w hereas middle cervical ganglion neurons received afferent inputs prima rily from cardiac mechanosensory neurites. It is concluded that the po pulations of neurons in different intrathoracic ganglia can display di fferential reflex control of cardiac function. Their redundancy in fun ction and noncoupled behavior minimizes cardiac dependency on a single population of intrathoracic neurons.