Response Analysis of Hemodynamics Parameters to Tyramine Infusion Post‐Exercise Training in Spountaneously Hypertensive Rats

The aim of the study was to assess the effects of exercise training in the vascular control after sympathetic stimulation mimicked by tyramine infusion in spontaneously hypertensive rats (SHR). Thirty two male SHR and wistar kyoto were submitted or not to a swimming protocol, resulting in four groups: sedentary normotensive (SN), trained normotensive (TN), sedentary hypertensive (SH) and trained hypertensive (TH). Arterial pressure (AP), heart rate (HR), power spectral analysis of HR (HRV), systolic AP variability (SAPV) and diastolic (DAPV) were recorded in baseline conditions. Following, the infusion of tyramine was administrated. Resting bradycardia was observed in both TN and TH rats compared with their respective sedentary animals. Exercise training attenuated AP in TH vs . SH. The variance of HRV was lower in SH vs . TH. The variance of SAPV and DAPV were higher in SH vs . TH. The LF component of HRV, SAPV and DAPV were lower in TH than SH. The pressor response to tyramine was enhanced in trained SHR but not kyoto. In conclusion, the results points to a sympatolitic effect of exercise training, probably at pre synaptic level, suggesting an up regulation of α_{1‐receptors in vascular smooth muscle. These findings showed that exercise training may be a therapeutic tool for improving function in hypertensive individuals.}