ASSESSMENT OF β-ADRENORECEPTOR ANTAGONISTIC ACTIVITY OF NS1 AND NS2 ON PERCENTAGE INHIBITION OF ISOPRENALINE INDUCED TACHYCARDIA AND HYPOTENSION IN RATS

The present investigation is carried out for β-adrenoreceptor antagonistic activity of both derivatives by evaluating their effects on the isoprenaline-induced tachycardia and hypotension in rats. Rats were divided into 5 groups (n=6) based on the treatment given to them. Group 1 received saline (0.9 % NaCl) only, groups 2, 3 were treated using test drugs NS1 and NS2 (1 mg/kg, i.v.) and groups 4, 5 received standard drugs propranolol (2 mg/kg, i.v.) and atenolol (1 mg/kg, i.v.). After 15 minutes of injection of drugs, the isoprenaline was injected, and the change in mean arterial pressure and heart rate were recorded. Administration of isoprenaline alone (0.3, 1 and 3 µg/kg, i.v.) produced significant dose-dependent hypotension and tachycardia to the rats. Pretreatment with NS1 and NS2 produced significant (p<0.01 and p<0.05 respectively) inhibition of isoprenaline-induced hypotension on normal rats. However, isoprenaline-induced tachycardia was significantly (p<0.05) reduced by NS1 pretreatment only. Propranolol showed significant (p<0.01) inhibition of isoprenaline-induced tachycardia and hypotension, while atenolol was significant (p<0.01) effective against inhibition of hypotension only. Results indicated that both derivatives, i.e. NS1 and NS2, have the potential to inhibit β receptors, but NS1 showed higher affinity to inhibit β1 receptors as compared to NS2. Hence study suggests that NS1 might have higher potency in β1 adrenoreceptor blocking activity.