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.


BM&L-May 2005