PMID: 3760771Sep 1, 1986Paper

Cholinergic action on the heart of the leech, Hirudo medicinalis

The Journal of Experimental Biology
R L Calabrese, A R Maranto

Abstract

Experiments were performed to determine the role of acetylcholine (ACh) in neuromuscular transmission in the heart of the leech Hirudo medicinalis. Superfused or iontophoretically applied ACh rapidly depolarized both isolated heart muscle cells and muscle cells in isolated hearts in a dose-dependent manner. the depolarization was associated with a conductance increase of the muscle membrane that had a reversal potential of -9 mV. Eserine potentiated the response to superfused ACh, reducing the threshold from 10(-6) to 10(-8) mol l-1. Acetylcholinesterase was localized histochemically to be in the immediate area of neuromuscular terminals. Superfused nicotinic agonists mimicked the effects of ACh, while superfused nicotinic antagonists reversibly blocked the iontophoretic response of heart muscle fibres to ACh. 5 X 10(-7) mol l-1 curare, 5 X 10(-5) mol l-1 nicotine and 1 X 10(-4) mol l-1 atropine reduced the iontophoretic response to half its original amplitude. Alpha-bungarotoxin did not block the response of heart muscle cells to iontophoretically applied ACh. Curare was used to determine whether the neurones that innervate the heart-HE motor neurones and HA modulatory neurone--use ACh as a neuromuscular transmitter. The fast ...Continue Reading

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