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 RESEARCH PAPER
Year : 2005  |  Volume : 37  |  Issue : 6  |  Page : 366-370

Effect of reactive oxygen species on cholinergic receptor function


Cancer, Aging and Metabolism Research Division, University College of Pharmaceutical Sciences, Kakatiya University, Warangal -506 009,Andhra Pradesh, India

Correspondence Address:
D R Krishna
Cancer, Aging and Metabolism Research Division, University College of Pharmaceutical Sciences, Kakatiya University, Warangal -506 009,Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0253-7613.19072

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OBJECTIVE: To investigate the role of reactive oxygen species (ROS) on cholinergic receptor function. MATERIALS AND METHODS : Rectus abdominis and isolated heart preparations of frog ( Rana tigirina ) were used to assess nicotinic and muscarinic receptor activity, respectively. Thirty percent hydrogen peroxide (H2O2) solution and Fenton mixture (Fm, 13.9 mg, 50 M of FeSO4, 75 mg of sodium EDTA and 50 L of 30% H2O2 were added to 10 ml of 0.1 M K2HPO4) were used to generate 1 mM H2O2 and hydroxyl free radicals. The responses were recorded with acetylcholine at different phases of exposure of tissues to ROS. Normal frog Ringer was used as a physiological solution. Responses of acetylcholine were also recorded in the presence of ROS before and after exposure of the tissue to an antioxidant (ascorbic acid). RESULTS : Free-radical-mediated receptor damage was dose (1-100 mM H2O2) and time (10-30 min) dependent when responses were taken with 30 g and 30 ng of ACh for nicotinic and muscarinic receptors, respectively. There was no effect of ROS on prior exposure of tissue to ascorbic acid (antioxidant) at a concentration of 300 g/ml. The antioxidant has not shown any beneficial effect on sulfhydryl groups of G-protein-coupled muscarinic receptors, which are more susceptible and sensitive to ROS than ion-channel nicotinic receptors where there is 96% protection with the antioxidant. Reactive oxygen species has shown different effects on receptor function. CONCLUSION: Free radicals continuously cause considerable damage to the receptors. G-protein-coupled muscarinic receptors are more susceptible than ion-channel-linked nicotinic receptors. Antioxidants are shown to play a major role in protecting free-radical-mediated receptor damage.






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