The depressor reflex arising from the left coronary artery of the cat.

1. The main left coronary artery of the cat was perfused through its own common carotid artery. Changes in perfusion pressure were produced from a pressurized reservoir.2. In cats anaesthetized with pentobarbital, increased coronary artery pressure always caused a reflex reduction of the discharge in sympathetic nerves. A reflex fall in blood pressure occurred less frequently. In cats anaesthetized with chloralose, increased coronary artery pressure caused a reflex bradycardia without any primary change in sympathetic activity.3. The afferent fibres of the coronary depressor reflex are in the vagus nerves. The efferent fibres were both sympathetic and vagal.4. It seems likely that the coronary depressor reflex is initiated by excitation of the coronary mechanoreceptors. It also seems likely that the reflex response to the intracoronary injection of 1 mug veratridine (Bezold-Jarisch effect) was initiated at least in part by excitation of these same receptors.