Does adenosine A1 receptor stimulation causes QRS prolongation by blocking beta adrenergic receptors in amitriptyline poisoning?

AimsTo investigate the role of beta receptor blockade via adenosine A1 receptor stimulation on amitriptyline-induced QRS prolongation.MethodsIsolated rat hearts were randomized into three groups (n = 8 for each group). After pretreatment with 5% dextrose (control) or DPCPX (8-cyclopentyl-1,3-dipropylxanthine), or propranolol + DPCPX, amitriptyline infusion was given to all groups. Intact beta adrenergic receptor response was verified with a bolus dose of isoproteranol (3 × 10−5 M).ResultsAmitriptyline (5.5 × 10−5 M) infusion following pretreatment with 5% dextrose or 10−4 M DPCPX prolonged QRS by 40–110% and 30–75%, respectively. After the beta receptor blockade with 10−2 M propranolol bolus, amitriptyline infusion following pretreatment with DPCPX prolonged QRS by 40–130%. Amitriptyline infusion following pretreatment with DPCPX (10−4 M) shortened the QRS at 40, 50 and 60  min significantly when compared to propranolol + DPCPX group (168.8 ± 4.9%, p < 0.05; 170.8 ± 6.9%, p < 0.01; 174.0 ± 6.9%, p < 0.01, respectively). Amitriptyline infusion following pretreatment with 5% dextrose prolonged QRS duration significantly at 50th minutes (209.5 ± 6.1%, p < 0.05) compared to DPCPX pretreatment group.ConclusionDPCPX pretreatment shortened amitriptyline-induced QRS prolongation. Beta adrenergic receptor blockade enhanced QRS prolongation shortened by DPCPX pretreatment. Adenosine A1 receptor stimulation related to beta adrenergic receptor blockade may play a role in amitriptyline-induced QRS prolongation in isolated rat hearts.