Innervation of bat heart: cholinergic and adrenergic nerves innervate all chambers

Adult Miniopterus schreibersii were anesthetized with chloroform, and in vitro preparations of cardiac chambers were prepared. Stimulation of intramural nerves in right ventricles paced at 6 Hz caused an inhibition (56.3 +/- 3.5% decrease on basal force) mediated by cholinergic nerves and an excitation (91.5 +/- 9.9% increase on basal force) mediated by adrenergic nerves. Mean pD2s (-log effective concentration, 50%) for ventricular beta-adrenoceptors and muscarinic cholinoceptors were 6.99 +/- 0.03 and 6.42 +/- 0.07, respectively. The inhibition of ventricular contractility, by nerve stimulation or exogenous acetylcholine, occurred even after blockade of beta-adrenoceptors. The results were comparable to those obtained on atria. In some experiments, the heart was perfused in situ and paced via electrodes on the ventricle: stimulation of the right vagus nerve decreased right ventricular contractility by up to 90%. The results show that, at least in this hibernating mammal, there is an adrenergic innervation of the ventricle. The presence of a cholinergic vagal innervation capable of inhibiting the basal force of ventricular contraction has not been shown in any other mammal.