Cholinergic Action on the Heart of the Leech, Hirudo Medicinalis

Abstract
Experiments were performed to determine the role of acetylcholine (ACh) in neuromuscular transmission in the heart of the leech Hirudo medicinalis. Our results indicate that heart muscle cells have nicotinic acetylcholine receptors that open in the presence of ACh, thereby increasing membrane conductance. The HE motor neurone is probably cholinergic and engages these receptors in its neuromuscular transmission, while the HA modulatory neurone is probably not cholinergic.