Indian red scorpion venom modulates spontaneous activity of rat right atria through the involvement of cholinergic and adrenergic systems.
Indian J Exp Biol
; 1999 May; 37(5): 455-60
Article
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| IMSEAR
| ID: sea-62326
ABSTRACT
The effect of Indian red scorpion (Mesobuthus tamulus concanesis, Pocock; MBT) venom was investigated on isolated rat right atrial preparations. MBT venom (0.001-3.0 micrograms/ml) exhibited a peculiar concentration-response pattern with respect to rate. The venom concentrations between 0.001-0.01 microgram/ml increased the atrial rate (phase I), followed by a relative decrease with 0.03-0.3 microgram/ml (phase II), and then an abrupt increase with 0.6-3.0 micrograms/ml (phase III). On the other hand, the force was unaltered by venom at phases I and II, while an increase was seen at phase III (3.0 micrograms/ml). Propranolol (0.1 microM) completely blocked the cardiostimulant action of venom at phase III. Further, this stimulant action of venom was absent in atria obtained from reserpinized animals. Pretreatment with atropine (0.3 microM), produced tachycardia at concentrations 0.1-0.3 microgram/ml of venom. But, hexamethonium (30 microM) had no influence on the venom (0.1 microgram/ml)-induced alterations in rate. However, MBT venom increased the acetylcholinesterase (AChE) activity (2-3 fold) in a concentration-dependent manner. Tetrodotoxin (2 microM), did not block the increase in rate produced by 0.01 microgram/ml of venom. Results suggest that, MBT venom-induced alterations of cardiac rhythmicity are mediated through cholinergic as well as adrenergic mechanisms depending upon the concentrations. The modulation of atrial rate at very low concentrations may be due to the direct action of venom on the atrium.
النص الكامل:
1
الفهرس:
IMSEAR
الموضوع الرئيسي:
Acetylcholinesterase
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Rats
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Reserpine
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Atropine
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Scorpion Venoms
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Tetrodotoxin
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Male
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Muscarinic Antagonists
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Hexamethonium
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Dose-Response Relationship, Drug
اللغة:
En
مجلة:
Indian J Exp Biol
السنة:
1999
نوع:
Article