Brain capillary perfusion in the spontaneously hypertensive rat during the wake-sleep cycle

Abstract

Hypertension is accompanied by circulatory changes in the brain and in other vascular districts; at disease onset, these changes may be largely functional and dependent on metabolic and vegetative drives. The wake-sleep cycle is a major physiological source of ultradian variability in autonomic function and in cerebral blood flow and metabolism. Aim of the study was to investigate whether sleep induces functional changes in the brain microcirculation in the developing hypertensive state. The fraction of brain capillaries perfused by plasma (perfused/anatomical capillaries) was assessed in young (8-10 weeks) spontaneously hypertensive rats (SHR) during quiet wakefulness, quiet sleep and active sleep. The density of anatomical capillaries was assessed in two groups of animals using both a histochemical method (alkaline phosphatase, AP, for morphometric measurements) and an immunofluorescence method (anti-fibronectin antibodies, FN, to detect all existing capillaries). The density of perfused capillaries was determined by intravascular injection of a fluorescent marker. The fraction of anatomical capillaries perfused by plasma was always close to maximal (0.96-0.97), without significant variations among the states of the wake-sleep cycle, and was the same for AP-stained and FN-stained sections. Data thus indicate that in this model of essential hypertension no functional changes in plasma perfusion of cerebral capillaries occur in the early stages of the disease.

Chronic Cerebral Hypoperfusion Protects Against Acute Focal Ischemia,Improves Motor Function, and Results in Vascular Remodeling

“…The cortex benefited more by enriched leptomeningeal collaterals than the subcortex. Since the rat capillary diameter was 4-6 m (Lee, 1995;Silvani et al, 2004), the vascular density measured in the present study represents only functional arteries, arterioles, and some large sized-capillaries. In a previous study, matrix metalloproteinase-2 activity was increased in brains preconditioned with chronic cerebral hypoperfusion, an indirect indication of vascular remodeling (Choi et al, 2007;Mabuchi et al, 2005).…”

Sleep and vascular disorders

“…In another study, brain capillary perfusion was examined during the sleep-wake cycle in young (8-10 weeks) SHR before blood pressure became elevated [2]. The purpose of studying the brain microcirculation in these animals was to find out whether capillary rarefaction, reported by other investigators in extracerebral organs of the SHR, was also present in the brain.…”

“…In another study, brain capillary perfusion was examined during the sleep-wake cycle in young (8-10 weeks) SHR before blood pressure became elevated [2]. The purpose of 0026-0495/$ -see front matter D…”

“…These interesting in vivo findings led to the conclusion that significant cardiac sympathovagal imbalance, with increased sympathetic modulation, occurs in the SHR during sleep. This imbalance is less evident during the waking hours.In another study, brain capillary perfusion was examined during the sleep-wake cycle in young (8-10 weeks) SHR before blood pressure became elevated [2]. The purpose of 0026-0495/$ -see front matter D…”

Cerebrovascular function in hypertension: Does high blood pressure make you old?

“…Comparing spontaneously hypertensive (SHR) to Wistar‐Kyoto (WKY) rats at early, mid, and late stage hypertension showed that reduction of arterial lumen diameter can occur early and continue while cerebral blood flow (CBF) and responsivity of CBF are increased in the early stages of hypertension, but reduced in later stages (Li et al., 2015). Remodeling in arteriolar and smaller vessels in the SHR, yet, may not occur until BP is at hypertensive levels (Silvani et al., 2004). It's possible that vessel remodeling may reduce the capability for flow augmentation to active neural tissue and hence, impact cognitive function.…”