Neural Accelerator Research Articles

Innervation and pharmacology of the heart of Urodacus, a scorpion

1. 1. The heart of the scorpion Urodacus is innervated by accelerator and inhibitor fibres. These run together through the first free ventral ganglion; some inhibitor fibres pass through more caudal ganglia. 2. 2. The response of the heart to eserine (isolated and innervated preparations, under neural acceleration or inhibition) indicates that cardiac inhibition is cholinergic, mediated by an unspecified choline ester. 3. 3. The inhibitory effect of applied acetylcholine takes place at a site different from that of neuronal inhibition. 4. 4. Atropine and d-tubocurarine had no effect at concentrations of 10 −4. 5. 5. The heart-rate is not affected by the distension of the myocardium. The pericardial cells are not involved in cardio-acceleration.