Suppressing cardiac vagal modulation and changing sleep patterns in rats after chronic ischemic stroke injury

Chronic autonomic function and sleep architecture changes in patients post-stroke are not well understood. Using wireless polysomnographic recordings, this study aimed to investigate the long-term effects on sleep patterns and autonomic function in free moving rats after middle cerebral artery occlusion (MCAO). The sleep pattern and heart rate variability (HRV) of Wistar-Kyoto rats (WKY) were analyzed. After 7-10days, the rats were divided into two groups: an MCAO group (n=8) and a sham surgery group (n=8). Compared with shams, MCAO rats showed decreased accumulated quiet sleep (QS) time over 24h during the 3rd week. The time percentage, duration and delta power of QS were also significantly decreased in the MCAO group during the dark period. Compared with baseline, there were significant increases in the parasympathetic-associated HRV measures in the sham group, including the total power (TP), high frequency power (HF) and lower frequency power (LF), throughout the post-operative weeks (primarily the 2nd and 3rd weeks), reflecting a developmental increase of parasympathetic modulation; the normalized LF and the LF-HF ratio were unaffected. In great contrast, however, most of the HRV measures in the MCAO group were not significantly changed. Therefore, this study showed that the long-term effects of ischemic stroke injury involve retardation of the establishment of parasympathetic enhancement and disturbance of the normal sleep-wake cycle.