Age related alterations in the response of the pial arterioles to adenosine in the rat.

To evaluate the effects of aging on vasoreactivity of pial arterioles to adenosine and barium chloride, an hydraulically intact cranial window preparation was developed in the rat. The microvasculature of anesthetized 3- and 24-month-old Fischer-344 rats was studied during superfusion with artificial cerebrospinal fluid with and without test agents and results determined by videomicroscopy techniques. In both cohorts, the response of pial arterioles to adenosine was both dose and vessel size dependent: arteriolar dilation increased with increasing concentrations of adenosine and at any given concentration the percent increase in diameter was greater in the smaller vessels. During adenosine superfusion the absolute changes and percent increase in vessel caliber were greater in the young rats. Arteriolar vasoconstriction due to barium chloride was vessel size dependent but there were no significant differences in response between young and aged rats. The results indicated an attenuated cerebrovascular response in aged rats to adenosine, but not to barium chloride. This may be due to a difference in the mode of action in these two compounds. Venules did not respond to adenosine at any concentration.