Influence of pH on Adenosine-Induced Dilatations of Pial Arteries
The release of adenosine from the brain during ischemia has been demonstrated and verified (1, 3). A further study has shown increased tissue concentrations of adenosine during hypoxia, hypotension, electrical stimulation of the cortex, and hyperventilation (8). In addition, the dilatatory action of adenosine at small pial arteries (less than 50 μ) has been assessed (1). It has further been shown that larger pial arteries contributing significantly to the regulation of cerebral vascular resistance also dilate dose dependently upon perivascular application of adenosine (11). All these data support the role of adenosine in the metabolic regulation of cerebral vascular resistance in addition to the other known factors such as H+, K+, Ca++, and osmolarity (2, 5, 9, 10). For several conditions under which an increase of adenosine in the brain tissue or the cerebrospinal fluid has been measured, (ischemia, prolonged hypoxia or hyperventilation) a concomitant decrease or increase in the pH of the fluid surrounding the vessels must be assumed. Changes in the perivascular pH are well known to determine the resistance to flow of pial arteries (5, 9). Since interactions between local factors, such as H+ and K+, at pial arteries have already been demonstrated (5), it was of interest to study the influence of changes in pH on adenosine-induced dilatations of pial arteries.
KeywordsDilatatory Effect Adenosine Concentration Concentration Response Curve Hypercapnic Acidosis Pial Artery
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