The microcirculation in experimental hypertension and aging

The purpose of this manuscript is to review the literature concerning the alterations in the microvasculature in experimental hypertension and aging. We also present new unpublished data and results where previous studies have not addressed important questions. The new studies were performed using a chronic cranial window to allow multiple observations of the cortical surface vasculature over time. In vivo video, microscopic techniques were used to study long-term changes in microvascular caliber (vasomotion). In some studies, a chronic, in-dwelling aortic catheter allowed chaotic analysis of short-term blood pressure and heart rate variations. In these new studies we demonstrated a reduction in number of small arteriolar endpoints per cortical surface area in the spontaneously hypertensive rat and in the old Brown-Norway rat. There was also a reduction in the number of arteriole-to-arteriole anastomotic connections in the older rat. These vascular changes in the old rat were revised or prevented by caloric restriction. In the old rat, there was also a reduction in the variability of blood pressure, heart rate and microvessel caliber (vasomotion). These studies suggest that there is an alteration in the morphology of the small arterioles in hypertension and aging, that may lead to reduced ability to perfuse cortical tissue. In addition, there appears to be a diminution of overall short-term cardiovascular and microvascular control.