The effects of periarterial nerve activation on coronary vessel tone in an isolated and perfused slab of beef ventricle

The direct effects of extrinsic nerve stimulation on coronary artery tone are unclear because of the complications arising from alterations in myocardial dynamics which themselves alter flow. An isolated and perfused nonbeating slab of beef ventricle was utilized in the present experiments to eliminate secondary complications and the efects of periarterial nerve activation on coronary perfusion pressure were examined. It was found that stimulation induced vasoconstrictor responses which were enhanced by physostigmine, a cholinesterase inhibitor, and blocked by atropine. These responses were duplicated by exogenous acetylcholine both in the perfused preparation and in isolated strips of coronary artery. Although added noradrenaline gave vasodilatation, no response attributable to the release of noradrenaline from nerves was obtained. It is concluded that the coronary vasculature of the beef receives a cholinergic innervation and that its activation, especially under conditions of reduced transmitter degradation, may induce considerable coronary vessel constriction.