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Impact of Intracardiac Neurons on Cardiac Electrophysiology and Arrhythmogenesis in an Ex Vivo Langendorff System
Published on: May 22, 2018
Cardiac input to medullary reticular formation: neuronal responses to CAO
Insights
Medullary reticular neurons show varied responses to coronary artery occlusions (CAO). These neurons often react differently to left anterior descending (LAD) and left circumflex (CX) artery occlusions, indicating differential processing of cardiac ischemia.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
- Autonomic Nervous System
Background:
- Medullary reticular formation neurons play a role in cardiovascular regulation.
- Cardiopulmonary sympathetic afferents convey information about the heart's status to the brainstem.
- Understanding neuronal responses to myocardial ischemia is crucial for deciphering cardiovascular reflexes.
Purpose of the Study:
- To investigate the responses of medullary reticular neurons to coronary arterial occlusions (CAO).
- To determine if these neurons respond differently to occlusions of distinct coronary arteries (left anterior descending vs. left circumflex).
- To compare neuronal responses to ischemia with responses to bradykinin administration.
Main Methods:
- Extracellular potentials were recorded from 46 medullary reticular neurons in anesthetized and paralyzed cats.
- Neurons responsive to electrical stimulation of cardiopulmonary sympathetic afferents were selected.
- Responses to coronary arterial occlusions (CAO) of the left anterior descending (LAD) and left circumflex (CX) arteries were analyzed.
Main Results:
- Twenty-four out of 46 neurons exhibited responses to CAO, characterized by excitation or inhibition during ischemia (IS response) or at occlusion onset/release (ON response).
- Neurons frequently displayed different response patterns to LAD versus CX artery occlusions.
- Thirty-one neurons showed similar qualitative responses to cardiac ischemia and epicardial bradykinin application.
Conclusions:
- Medullary reticular neurons exhibit differential responses to occlusions of different coronary arteries.
- These findings suggest distinct neural processing pathways for ischemia in different regions of the heart.
- Medullary neuronal activity during ischemia may be modulated by factors similar to those affected by bradykinin.
Abstract:
Responses of 46 medullary reticular neurons to coronary arterial occlusions (CAO) of the left anterior descending (LAD) and left circumflex (CX) coronary arteries were determined in chloralose-anesthetized cats paralyzed with pancuronium. Extracellular potentials were recorded from individual neurons, in the medial reticular formation, responsive to electrical stimulation of cardiopulmonary sympathetic afferents. CAO responses were characterized by one of three patterns. Cell activity changed during myocardial ischemia (IS response). Fifteen neurons were excited during ischemia (9 +/- 2.8 to 15 +/- 3.2 spikes/s for CX occlusion and 10 +/- 3.0 to 17 +/- 4.7 spikes/s for LAD occlusion), and two were inhibited (8 +/- 3.0 to 4 +/- 3.0 spikes/s). Cell activity changed at the onset or release of occlusion and rapidly adapted (ON response). Four cells were excited at the onset of LAD occlusion (2 +/- 1.4 to 10 +/- 6.0 spikes/s), 9 cells were excited at onset of CX occlusion (5 +/- 2.5 to 16 +/- 5.6 spikes/s), and 1 cell decreased its rate at onset of CX occlusion. A combination of ON and IS responses occurred in five cells (ON-IS response). Overall, 24 neurons exhibited at least one of these responses, and 22 cells were unaffected by CAO. Thirty neurons were tested for responses to CAO of CX and LAD; neurons most often exhibited different patterns of responses to CAO of each artery. Thirty-one of 34 cells tested exhibited qualitatively, but often not quantitatively, similar responses to cardiac ischemia and to application of bradykinin to epicardium of free wall of left ventricle. Results indicate that medullary neurons often respond differentially to occlusion of different coronary arteries.(ABSTRACT TRUNCATED AT 250 WORDS)
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