Abstract
Modest recovery of somatic function after incomplete spinal cord injury (SCI) has been widely demonstrated. Recently we have shown that spontaneous recovery of baroreflex regulation of sympathetic activity also occurs in rats. Dietary restriction in the form of every other day fasting (EODF) has been shown to have beneficial effects on the recovery of motor function after SCI in rats. The goal of this study was to determine if EODF augments the improvement of baroreflex regulation of sympathetic activity after chronic left thoracic (T8) surgical spinal hemisection. To determine this, we performed baroreflex tests on ad-lib fed or EODF rats 1 week or 7 weeks after left T8 spinal hemisection. One week after T8 left hemisection baroreflex testing revealed that gain of baroreflex responsiveness, as well as the ability to increase renal sympathetic nerve activity (RSNA) at low arterial pressure, was significantly impaired in the ad-lib fed but not the EODF rats compared with sham lesioned control rats. However, baroreflex tests performed 7 weeks after T8 left hemisection revealed the inability of both ad-lib and EODF rats to decrease RSNA at elevated arterial pressures. While there is evidence to suggest that EODF has beneficial effects on the recovery of motor function in rats, EODF did not significantly improve the recovery of baroreflex regulation of sympathetic activity.
Highlights
Moment-to-moment regulation of blood pressure is controlled by baroreceptor regulation of sympathetic and parasympathetic activity (Heymans and Neil, 1958; Dampney et al, 2002)
While every other day fasting (EODF) has been shown to augment the recovery of motor and sensory function after Spinal cord injury (SCI) (Plunet et al, 2008, 2010; Jeong et al, 2011), data on the extent of recovery of sympathetic cardiovascular regulation are limited
Based on studies from our laboratory to show recovery of baroreflex control of sympathetic activity after chronic SCI (Zahner and Schramm, 2011; Zahner et al, 2011; Castillo et al, 2012), as well as studies to suggest that caloric restriction augments baroreflex responsiveness in the naïve rat with intact spinal cords (Herlihy et al, 1992; Thomas et al, 1993), it was our intent to determine if EODF augments the recovery of baroreflex regulation of sympathetic activity after SCI
Summary
Moment-to-moment regulation of blood pressure is controlled by baroreceptor regulation of sympathetic and parasympathetic activity (Heymans and Neil, 1958; Dampney et al, 2002). Because the sympathetic pathways caudal to the site of injury, as well as the absence of tonically active descending inhibitory pathways are interrupted, blood flow is shunted to vasodilated areas above the site of injury This inappropriate shunting of blood from the lower extremities results in flushing, sweating, pounding headache, and in some cases seizure, and stroke. Both orthostatic hypotension and autonomic dysreflexia result from interruption of descending sympathetic spinal pathways and impair regulation of spinal sympathetic neurons caudal to the lesion (Osborn et al, 1990; Mayorov et al, 2001; Weaver et al, 2001, 2006; Gao et al, 2002; Krassioukov and Claydon, 2006)
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