Differential selectivity of cardiac neurons in separate intrathoracic autonomic ganglia

Abstract

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 ∼80% of intrinsic cardiac neurons and ∼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.

Dorsal spinal cord stimulation obtunds the capacity of intrathoracic extracardiac neurons to transduce myocardial ischemia

“…This neuron population forms the substrate for the processing of cardiovascular afferent information within peripheral autonomic ganglia, even when such ganglia are disconnected from the influence of central neurons (4,7). Local circuit neurons transduce cardiovascular afferent information reflexly to modulate the sympathetic and parasympathetic efferent outflows to cardiac effector sites (11). This population also receives significant descending inputs from central neurons (9,28,41).…”

“…The left middle cervical ganglion was identified and left in place, attached to surrounding tissues to maintain its stability. The activity generated by neurons in that ganglion was identified by using methods that have been described previously (6,11). The recording microelectrode utilized had a 250-m shank diameter, an exposed tip of 10 m, and an impedance of 9 -11 M⍀ at 1,000 Hz (model ME 25-10-2; Frederick Haer).…”

“…The activity generated by individual neuronal somata was identified by the amplitude and configuration (waveform recognition) of the recorded action potentials via the Spike 2 program. Using these techniques and criteria, action potentials generated by individual cell bodies and/or dendrites rather than axons of passage can be recorded for extended period of time (6,11). As such, once an active locus was identified the activity generated by its spontaneously active neurons was studied throughout the duration of the various protocols outlined below (cardiac stressors).…”

“…Intrathoracic extracardiac neurons are in constant communication with intrinsic cardiac ones in the overall coordination of regional cardiac indices (3,11). Neurons in intrathoracic extracardiac ganglia receive major inputs from the spinal cord preganglionic neurons that are under the control of the intermediolateral cell column that, in turn, receives inputs from spinal and supraspinal components of the cardiac neuronal hierarchy (2,20).…”

Nicotinic mechanisms in the autonomic control of organ systems

“…In the past decade it has become evident that these intracardiac ganglionated plexuses contain both cholinergic and adrenergic neurons, as well as interneurons and sensory afferents (Ardell and Randall, 1986;Blomquist et al, 1987;Moravec and Moravec, 1987;Ardell et al, 1988;Gagliardi et al, 1988;Armour and Hopkins, 1990). After removal of all their extracardiac neuronal inputs intracardiac neurons retain their ability for synaptic interactions suggesting that local reflexes may control cardiac dynamics independent of the CNS (Murphy et al, 1994;Armour et al, 1998;Thompson et al, 2000).…”