EFFECT OF CAFFEINE ON CEREBRAL BLOOD
FLOW
A
lot of studies have examined and well documented caffeine psychoactive effects,
but little is known about the effects of caffeine on cerebral blood flow
related to brain activity.
Joseph
R. Meno and his co-workers from Mount Sinai Hospital (New York) and Washington
University in Seattle (Effect of caffeine on cerebral
blood flow response to somatosensoy stimulation. Journal of Cerebral Blood
Flow and Metabolism 25, 775-784, 2005)
evaluated the effects of caffeine, an adenosine receptor antagonist, on
intracerebral arterioles in vitro and subsequently on the pial circulation
in vivo during cortical activation induced by contra-lateral sciatic
nerve stimulation.
In
their in vitro studies, the authors utilized isolated intracerebral
arterioles to determine the effects of caffeine (10 or 50 micro-mol/L) on
adenosine induced vasodilatation.
In
vivo they evaluated the pial arteriolar
response during cortical activation caused by contra-lateral sciatic nerve
stimulation after administering caffeine intravenously (0, 5, 10, 20, 30 and 40
mg/kg). The pial circulation was observed through a closed cranial window in chloralose-anesthetized
Sprague-Dawley rats.
Intravenous
administration of caffeine at the lowest dose studied (5mg/kg) had no effect on
either resting arteriolar diameter or stimulation-induced vasodilatation.
However at higher doses (10, 20, 30, 40 mg/kg) caffeine attenuated both resting
diameter and cerebral blood flow responses to somatosensory stimulation.
Meno’s
study shows that caffeine significantly reduces cerebrovascular responses to
both adenosine and to somatosensory stimulation and supports a role of
adenosine in the regulation of CBF during functional neuronal activity.