Role of Vasopressin on Intrinsic Cardiac Activity in Conscious Wistar Rats.

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BackgroundThe effects of vasopressin on cardiac chronotropism are controversial in different species.ObjectiveTo investigate if vasopressin can influence the cardiac intrinsic activity in conscious Wistar rats.MethodsAll the procedures of this study were approved by the Animal ethics committee (protocol #02/2016). Adult male Wistar rats underwent to a cannulation of the femoral artery and vein for mean arterial pressure (MAP) and heart rate (HR) recordings and drug infusions, respectively, in conscious rats, 24 h after the surgical procedures. After baseline recordings, i.v. atropine 2 mg/kg and i.v. metoprolol 1.7 mg/kg were injected with 5 min interval. After 10 min, i.v. vasopressin 0.0625 mg/mL/5 min (N=6) or saline (1 mL/5 min) (N=6) were infused and the variables were recorded for additional 10 min. Gene and protein expression of V1a, V1b and V2 subtype receptors for AVP were also carried in the right atrium by qPCR and Western Blotting, respectively. The AVP receptor subtypes were also labeled by immunofluorescence technique in the right atrium.ResultsVasopressin evoked bradycardic (−51±5 bpm) and pressor responses (39±6 mmHg) compared to baseline post‐autonomic blockade (130 ±8 mmHg and 406±16 bpm). Saline did not change HR (1±4 bpm) and MAP (−3±1 mmHg) compared to baseline after autonomic blockade (120±5 mmHg and 411±52 bpm). All subtypes of AVP receptors were expressed in the right atrium by qPCR, Western Blotting and immunofluorescence.ConclusionThe bradycardia elicited by vasopressin after cardiac autonomic blockade suggests that vasopressin can affect the cardiac intrinsic activity binding to the receptors in the right atrium.Support or Funding InformationFinancial support: FAPESP, CNPq and NEPAS‐FMABC.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.