Effects of cholinomimetic drugs on reptilian atrial muscles
Ojewole, J.A.; Akinwande, K.I.
Methods and Findings in Experimental and Clinical Pharmacology 6(7): 379-387
1984
ISSN/ISBN: 0379-0355 PMID: 6503473 Document Number: 238720
The effects of some cholinomimetic drugs were examined on isolated atria of rainbow lizards (Agama agama) and land tortoises (Kinixys spp.). Acetylcholine (ACh, 10-8-5 .times. 10-5 M) caused concentration-dependent, atropine-sensitive, negative chronotropic or inotropic responses in isolated spontaneously-beating right or electrically-driven left atria of rainbow lizards and land tortoises. This prototype cholinergic drug (ACh, 10-8-5 .times. 10-5 M) also induced atropine-sensitive, concentration-related negative chronotropic or inotropic responses in isolated atrial muscles taken from guinea pigs. Histamine (10-8-5 .times. 10-5 M) produced concentration-related positive chronotropic or inotropic responses in isolated spontaneously-beating right or electrically-driven left atria of rainbow lizards and guinea pigs without significantly affecting (P > 0.05) the tortoise atria. 5-Hydroxytryptamine (5-HT, 10-7-5 .times. 10-5 M) induced concentration-dependent positive chronotropic or inotropic responses in isolated, spontaneously-beating right or electrically-driven left atria of rainbow lizards, tortoises and guinea pigs. Nicotine (10-8-5 .times. 10-5 M) had no effect on the rate of beating of the lizard or tortoise isolated right atria, but caused concentration-dependent positive chronotrophic responses in spontaneously-beating isolated right atria of the guinea pig. Nicotine (10-8-5 .times. 10-5 M) had no effect on contractile tension of isolated, electrically-driven left atria of the tortoise; it induced a biphasic inotropic response in driven left atria of the rainbow lizard and produced a concentration-related positive inotropic response in electrically-driven isolated left atria of the guinea pig. The use of rainbow lizard and tortoise atrial muscle strips as laboratory models for routine pharmacological evaluation of cholinergic and adrenergic drugs, especially in tropical African countries where these harmless, cheap reptiles abound, is strongly advocated.