Conflict of Interest Dr. Roger serves as a consultant to Medtronic and Globus. No financial or material support was received in conjunction with this work.
Male Wistar-Kyoto (WKY) rats, 3 months of age, were obtained from the animal facilities of the Biomedical Sciences Institute – Department of Physiology and Biophysics, University of Sao Paulo, Brazil. The rats were housed individually in a synchronized 12-h light–dark cycle (light: 6 am to 6 pm, 200 lux; dark 6 pm to 6 am, <0.1 lux), and temperature controled room (22 ± 2°C) at least 2 weeks prior to the

experiments. A standard rat diet and tap water were supplied ad libitum. All experimental protocols were performed in accordance with the Inhibitors,research,lifescience,medical ethical principles in animal research of the Brazilian College Inhibitors,research,lifescience,medical of Animal Experimentation, guidelines for the human use of laboratory animals by the State of Sao Paulo and approved by the Ethical Committee of the Biomedical Sciences Institute of the University of Sao Paulo. Measurements of cardiovascular parameters For blood pressure and HR recordings, catheters were implanted into the left femoral artery, and for drug administration, catheters were placed into the left femoral vein under anesthesia with ketamine–xylazine (70:6 mg/kg im). The catheter was tunneled subcutaneously Inhibitors,research,lifescience,medical and attached to the back muscles of the neck. Catheters were implanted 24

h before the experiments to allow a complete recovery from anesthesia. Arterial pressure and HR were recorded by connecting Inhibitors,research,lifescience,medical the arterial catheter to a flow-through pressure transducer (P23XL, Gould, Cleveland, OH), which was then connected to a recording system (carrier amplifier + Biotach, RS 3400 recorder

Gould). The rat was allowed to rest for stabilization of cardiovascular parameters. Evaluation of baroreflex bradycardia and tachycardia Arterial baroreceptors were Inhibitors,research,lifescience,medical stimulated by a series of increasing doses of intravenous injections of phenylephrine (PE) and sodium nitroprusside (SNP). Response logistic function curves of MAP and HR were obtained. The baseline values and peak changes of MAP and HR were analyzed. The reflex test with Oxalosuccinic acid progressive doses of PE and SNP lasted for about 30–40 min. MAP and HR were recorded continuously and the mean baseline values of blood pressure and HR (between the responses obtained to different doses) used for plotting the midpoint of the curves. PE injections (0.1, 0.2, 0.4, 0.8, 1.6, 3.2, 6.4, 12.8 μg/kg) and SNP (0.2, 0.4, 0.8, 1.6, 3.2, 6.4, 12.8, 25.6 μg/kg) were randomized. Also, DNA-PK function melatonin infusions were randomized. Melatonin administration Both baseline values and responses to load/unload of baroreceptors with bolus of PE and SNP, respectively, were recorded during continuous intravenous infusion of either vehicle (10−7 V:V of alcohol in saline 0.9%, at a rate of 0.65 mL/h) or of melatonin (0.43 × 10−9 mol/L, at a rate of 0.65 mL/h) for 30 min, which was light protected throughout the experiment.