Activity of in situ stellate ganglion neurons of dogs recorded extracellularly

Abstract

Activity was recorded from 145 neurons in the in situ stellate ganglia of 36 dogs. The activity of 28 of these neurons, most of them located in the ganglia's cranial medial region, was related to the cardiac cycle primarily during systole. The activity of 16 of these cardiovascular-related neurons was modified by gentle mechanical distortion of the superior vena cava (1), heart (4), or thoracic aorta (11). Forty-one of the neurons were modified by respiration, with 17 being phase-locked to the respiratory cycle. Other neurons were activated by gentle mechanical distortion of localized regions of the thoracic wall (21% of all neurons), neck (18%), skin of the left foreleg (10%), or the mediastinum adjacent to the stellate ganglion (3%). Acutely decentralizing the stellate ganglion abolished the spontaneous activity of some, but not all, of these neurons including the respiratory or cardiovascular-related neurons. In the intact or acutely decentralized stellate ganglion, few neurons were activated by single short duration (1-4 ms) stimuli delivered to nerves attached directly or indirectly to the ganglion; however, most were activated by brief high frequency stimuli delivered in trains of 20-200 ms, or by single stimuli lasting 20-200 ms. As most cardiovascular, respiratory, or neck-related neurons in the stellate ganglion were not activated by single brief stimuli delivered to the cardiopulmonary nerves or vagosympathetic trunks, presumably they did not project their axons into the neck or thoracic organs. Thus, they were considered to be interneurons. It is postulated that interneurons in stellate ganglia can be modified by afferent receptors located in tissues of the neck, lungs, heart, or great thoracic vessels, whether the ganglion is intact or acutely decentralized. In addition, neurons in the stellate ganglion can be modified by mechanoreceptors located in the thoracic wall, abdominal wall, foreleg, or adjacent mediastinum. The majority of these neurons are activated by trains of impulses rather than single short duration impulses.

In vivo extracellular recording of sympathetic ganglion activity in a chronic animal model

“…Similarly, afferent input to the ganglia, arising from cardiac and extracardiac anatomical structures, affects the electrical activity of various neuronal populations in the ganglia. These conclusions derive from data accumulated in electrophysiological animal studies performed in vitro [12,24], in situ [4,5,9,13] and in vivo [3,8], which examined the autonomic ganglia activity in relation to cardiovascular and respiratory functions. In these studies, the electrical activity obtained from individual autonomic ganglia cells was recorded using intracellular microelectrodes [3,8,9,13].…”

“…In these studies, the electrical activity obtained from individual autonomic ganglia cells was recorded using intracellular microelectrodes [3,8,9,13]. An alternative approach was the determination of ganglionic activity by extracellular bipolar electrodes mounted on nerves entering or exiting the ganglia [4,5,13].…”

“…In cats and dogs, specific cardiac and respiratory events activate some of the neurons, including cells of the middle cervical and stellate ganglia [5,7,13]. For instance, the spikes of certain neurons are phase-linked to the isovolumetric contraction stage of the cardiac cycle [5], other units fired during isovolumetric relaxation [5], while a third category of neurons were activated by increasing the positive respiratory pressure [10].…”

“…In cats and dogs, specific cardiac and respiratory events activate some of the neurons, including cells of the middle cervical and stellate ganglia [5,7,13]. For instance, the spikes of certain neurons are phase-linked to the isovolumetric contraction stage of the cardiac cycle [5], other units fired during isovolumetric relaxation [5], while a third category of neurons were activated by increasing the positive respiratory pressure [10]. In order to validate the reciprocal linkage between the ganglionic neuroelectrical activity and function of appropriate organs, various mechanical, pharmacological, and electrophysiological manipula- tions were performed, while investigating with microelectrodes the activity of several single ganglion cells [5,8,13].…”

“…For instance, the spikes of certain neurons are phase-linked to the isovolumetric contraction stage of the cardiac cycle [5], other units fired during isovolumetric relaxation [5], while a third category of neurons were activated by increasing the positive respiratory pressure [10]. In order to validate the reciprocal linkage between the ganglionic neuroelectrical activity and function of appropriate organs, various mechanical, pharmacological, and electrophysiological manipula- tions were performed, while investigating with microelectrodes the activity of several single ganglion cells [5,8,13]. Stimulation of afferent and efferent nerves before and after decentralization was an additional strategy used to identify the connections of various nerves, and to localize their somata in the ganglia [3,5,8,9,13].…”