Efferent pathways of the coronary chemoreflex

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Regulation

Background:

• The coronary chemoreflex is a neural reflex originating in the heart.
• Understanding its efferent pathways is crucial for comprehending cardiovascular control.

Purpose of the Study:

• To identify the efferent pathways mediating vasodilation during coronary chemoreflex activation.
• To compare these reflex responses in skeletal muscle versus skin vasculature.

Main Methods:

• In vivo canine model using innervated, perfused gracilis muscle and hindpaw.
• Coronary chemoreflex activation via intracoronary nicotine injections.
• Pharmacological blockade with atropine, tripelennamine, propranolol, and guanethidine.

Main Results:

• Coronary chemoreflex activation induced significant vasodilation in skeletal muscle but minimal vasodilation in paw (skin).
• Guanethidine blocked vasodilation in muscle, indicating withdrawal of adrenergic tone.
• Pharmacological agents did not implicate sympathetic cholinergic pathways in this reflex.

Conclusions:

• The coronary chemoreflex-induced vasodilation in skeletal muscle is mediated by withdrawal of sympathetic adrenergic tone.
• Sympathetic cholinergic pathways are not involved in coronary chemoreflex-mediated vasodilation in skeletal muscle.
• The coronary chemoreflex elicits a greater withdrawal of adrenergic tone and vasodilation in skeletal muscle compared to skin.