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|Title:||Influence of chronic treatment of rats with isoprenaline and calcium channel blockers on response of isolated right ventricle to noradrenaline|
|Abstract:||Influence of chronic treatment of rats with and calcium channel blockers (CCBs) and isoprenaline (ISP) on responses to noradrenaline (NA) was investigated on electrically - driven isolated right ventricle preparations. The ventricles were obtained from animals treated with chronic ISP or CCBs alone and chronic nifedipine, verapamil, diltiazem or nimodipine plus chronic ISP. A decreased response to NA as evidenced by an increase in EC50 for contraction which was observed in chronic ISP- treated preparations may be due to development of desensitisation (down-regulation) of beta-adrenoceptors. In chronic CCB-treated preparations there was a significant decrease in the EC50 of NA and decreased contractile response suggesting an increase in the beta-adrenoceptors and decreased availability of calcium, respectively . In chronic CCBs + ISP treated preparations further decreases in the EC50 values were observed suggesting that the voltage gated L-type Ca2+ channels may be affected directly or indirectly by change in beta-adrenoceptor activity. By the above results a proposed mechanism of interrelationship of beta-adrenoceptors with voltage gated L - type calcium channels in cardiac muscle is supported.|
|ISSN:||0975-1009 (Online); 0019-5189 (Print)|
|Appears in Collections:||IJEB Vol.39(03) [March 2001]|
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