Differential selectivity of cardiac neurons in separate intrathoracic autonomic ganglia

Analyses of activity generated by neurons in middle cervical or stellate ganglia versus intrinsic cardiac ganglia were performed to determine how neurons in different intrathoracic ganglia, which are involved in cardiac regulation, interact. Discharges of 19% of intrathoracic extracardiac neurons and 32% of intrinsic cardiac neurons were related to cardiodynamics. Epicardial touch increased the activity generated by approximately 80% of intrinsic cardiac neurons and approximately 60% of extracardiac neurons. Both populations responded similarly to epicardial chemical stimuli. Activity generated by neurons in intrinsic cardiac ganglia demonstrated no consistent short-term relationships to neurons in extracardiac ganglia. Myocardial ischemia influenced extracardiac and intrinsic cardiac neurons similarly. Carotid artery baroreceptors influenced neurons in ipsilateral extracardiac ganglia. After decentralization from the central nervous system, intrinsic cardiac neurons received afferent inputs primarily from cardiac chemosensitive neurites, whereas middle cervical ganglion neurons received afferent inputs primarily from cardiac mechanosensory neurites. It is concluded that the populations of neurons in different intrathoracic ganglia can display differential reflex control of cardiac function. Their redundancy in function and noncoupled behavior minimizes cardiac dependency on a single population of intrathoracic neurons.