TY - JOUR
T1 - Effect of 2-chloroadenosine on cerebrovascular reactivity to hypercapnia in newborn pig
AU - Gidday, J. M.
AU - Park, T. S.
PY - 1992
Y1 - 1992
N2 - The effect of local administration of vasodilative concentrations of the adenosine receptor agonist 2-chloroadenosine (2-CADO) on the hyperemic responses of the pial and parenchymal microcirculations to graded hypercapnia was determined. The cranial window and brain microdialysis-hydrogen clearance techniques were utilized in two groups of isoflurane-anesthetized newborn pigs to measure changes in pial diameters and local CBF, respectively, in response to graded hypercapnia in the absence and presence of 2-CADO. Progressive size-dependent dilations of pial arterioles [small = 41 ± 7 μm (mean ± SD), intermediate = 78 ± 13 μm, and large = 176 ± 57 μm in diameter] occurred in response to graded hypercapnia alone (P(a)CO2 = 58 and 98 mm Hg) and to superfusions of 2-CADO (10-5 M) during normocapnia; the magnitude of the dilative response to each of these stimuli was inversely proportional to vessel size. When hypercapnia was induced concomitantly with 2-CADO superfusion, the dilative effects of each stimulus were directly additive. Similarly, local microdialysis infusion of 10-5 M 2-CADO, which doubled CBF during normocapnia, did not affect the hyperemic response of the parenchymal circulation to graded hypercapnia (P(a)CO2 = 69 and 101 mm Hg). Our findings are consistent with the participation of adenosine in the mediation of cerebral hypercapnic hyperemia. If, however, adenosine is not involved in this dilative response, our results indicate that concomitant vascular and neuromodulatory actions induced by adenosine receptor stimulation do not affect the mechanism responsible for the hypercapnic hyperemic response.
AB - The effect of local administration of vasodilative concentrations of the adenosine receptor agonist 2-chloroadenosine (2-CADO) on the hyperemic responses of the pial and parenchymal microcirculations to graded hypercapnia was determined. The cranial window and brain microdialysis-hydrogen clearance techniques were utilized in two groups of isoflurane-anesthetized newborn pigs to measure changes in pial diameters and local CBF, respectively, in response to graded hypercapnia in the absence and presence of 2-CADO. Progressive size-dependent dilations of pial arterioles [small = 41 ± 7 μm (mean ± SD), intermediate = 78 ± 13 μm, and large = 176 ± 57 μm in diameter] occurred in response to graded hypercapnia alone (P(a)CO2 = 58 and 98 mm Hg) and to superfusions of 2-CADO (10-5 M) during normocapnia; the magnitude of the dilative response to each of these stimuli was inversely proportional to vessel size. When hypercapnia was induced concomitantly with 2-CADO superfusion, the dilative effects of each stimulus were directly additive. Similarly, local microdialysis infusion of 10-5 M 2-CADO, which doubled CBF during normocapnia, did not affect the hyperemic response of the parenchymal circulation to graded hypercapnia (P(a)CO2 = 69 and 101 mm Hg). Our findings are consistent with the participation of adenosine in the mediation of cerebral hypercapnic hyperemia. If, however, adenosine is not involved in this dilative response, our results indicate that concomitant vascular and neuromodulatory actions induced by adenosine receptor stimulation do not affect the mechanism responsible for the hypercapnic hyperemic response.
KW - Adenosine
KW - Carbon dioxide
KW - Cerebral blood flow
KW - Pial arteriole
UR - http://www.scopus.com/inward/record.url?scp=0026720745&partnerID=8YFLogxK
U2 - 10.1038/jcbfm.1992.90
DO - 10.1038/jcbfm.1992.90
M3 - Article
C2 - 1618943
AN - SCOPUS:0026720745
VL - 12
SP - 656
EP - 663
JO - Journal of Cerebral Blood Flow and Metabolism
JF - Journal of Cerebral Blood Flow and Metabolism
SN - 0271-678X
IS - 4
ER -