Cardiovascular response to stress after middle cerebral artery occlusion in rats

Previously, we have shown cardiovascular and autonomic disturbances in male Wistar rats following middle cerebral artery occlusion (MCAO). Using this model, neurochemical changes, that were maximal at 3-5 days and subsiding by day 10, were observed unilaterally in the insular cortex and amygdala. The amygdalar neurochemical changes may be related to the stroke-induced cardiovascular disturbances, since the amygdala is critical in mediating the cardiovascular responses to stress. We examined the cardiovascular responses to intermittent and continuous noise and air-jet stimulation in male Wistar rats on days 2-10 after right-sided MCAO or sham MCAO. Compared to the sham MCAO rats, intermittent noise elicited significant tachycardiac responses on days 5 and 7 after stroke. Air-jet stimulation also elicited a significant tachycardic response on day 5, whereas continuous noise produced significant tachycardiac and pressor responses at days 5 and 7, respectively, in the MCAO rats compared to the control rats. Analyses on the heart rate variability using fast Fourier transformation revealed significant increases in the normalized mid-frequency spectral power on day 7 for intermittent noise and air-jet stimulation, suggesting increases in the sympathetic activity. These results indicate a time-course of exaggerated cardiovascular responses to stress and suggest a state of susceptibility to cardiac perturbations in rats following stroke.