Response analysis of hemodynamics parameters to tyramine infusion post‐physical training in spountaneously hypertensive rats (546.5)

Abstract

The aim of the present study was to assess the effects of exercise training in the vascular control after sympathetic stimulation by tyramine infusion in spontaneously hypertensive rats (SHR). 33 male SHRs and WKY were submitted or not to a swimming protocol during 8 weeks, resulting in four groups: sedentary normotensive (SN, n=7), trained normotensive (TN, n=8), sedentary hypertensive (SH, n=8) and trained hypertensive (TH, n=10) rats. Arterial pressure (AP), heart rate (HR), means of power spectral analysis of HR (HRV), systolic AP variability (SAPV) and diastolic (DAPV) were recorded in baseline conditions. Following, the infusion of tyramine in three doses was administrated. Exercise training attenuated AP in TH vs. SH (p<0.001). The variance of HRV was lower in SH vs. TH (p=0.018). The other hand, the variance of SAPV and DAPV were higher in SH vs. TH (p=0.05). The LF component of HRV, SAPV and DAPV were lower in TH than SH (p<0.05). LF/HF was lower in TH than SH (p<0.05). The TN and TH presented an increased parasympathetic modulation compared with SN and SH (p<0.05). Pressor response to tyramine was enhanced in TH, but not in WKY. In conclusion, the results points to a sympatolitic effect of exercise training. This conclusion is supported by the impaired tyramine pressor response, suggesting an up regulation of α1‐receptors in vascular smooth muscle, once the administration of an agonist showed enhanced and the norepinephrine releaser showed impairment or the pressor response. These findings suggest that exercise training may be a therapeutic tool for improving function in hypertensive individuals.