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Effect of cholinergic antagonists on the bradycardic response of limpets to copper
Authors:A?M?Pugliese  G?Bini  M?De?Pirro  G?Pepeu  Email author" target="_blank">G?ChelazziEmail author
Institution:(1) Department of Preclinic and Clinic Pharmacology, University of Florence, 50139 Florence, Italy;(2) Department of Animal Biology and Genetics, University of Florence, 50125 Florence, Italy
Abstract:The effect of cholinergic antagonists on the bradycardia induced by waterborne copper in the Mediterranean limpet Patella caerulea was investigated by using non-invasive recording of cardiac activity of whole animals. Preliminary tests were conducted to check the role of cholinergic and serotoninergic systems in the control of heart rate of P. caerulea. Superfusing the whole limpets with carbachol (cholinergic agonist) at 5×10–5 M produced a negative inotropic and chronotropic effect (bradycardia), while superfusion with 5-hydroxytryptamine produced a positive inotropic and chronotropic effect (tachycardia). Exposure of limpets to a solution of copper in artificial seawater (0.25 mg l–1, 3 h) reduced their heart rate to about 80% the value recorded in copper-free water. This bradycardia was inhibited by injecting the limpets with atropine (cholinergic muscarinic antagonist) at 21 mgrg g–1 wet flesh weight and with benzoquinonium cholinergic nicotinic antagonist blocking the K+ mediated acetylcholine (ACh) response] at 10 and 100 mgrg g–1 prior to copper exposure. In contrast, D-tubocurarine (cholinergic nicotinic antagonist blocking Na+ mediated ACh response) had no effect at 85 mgrg g–1. These results agree with the involvement of the cholinergic system in the bradycardic response of limpets to copper, and support the view that gastropod ACh receptors do not fit the vertebrate nicotinic–muscarinic classification.Communicated by R. Cattaneo-Vietti, Genova
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