Background-Cerebral blood now is tightly coupled to neuronal metabolic
activity, a phenomenon referred to as functional hyperemia. The mecha
nisms underlying functional hyperemia in the brain have been extensive
ly studied, but the link between neuronal activation and nutritive blo
od now has yet to be defined. Recent investigations by our laboratory
and others have identified a potential role for astrocytes as an inter
mediary cell type in this process. Summary of Review-This short review
will develop the hypothesis that cytochrome P450 epoxygenase activity
in astrocytes catalyzes formation of epoxyeicosatrienoic acids (EETs)
, which act as potent dilators of cerebral vessels and are released in
response to glutamate receptor activation within astrocytes. Neuronal
activity stimulates release of arachidonic acid from the phospholipid
pool of astrocytic membranes. We provide evidence that the arachidoni
c acid released on stimulation of glutamate receptors within astrocyte
s is metabolized by cytochrome P450 2C11 cDNA enzymes into EETs. Concl
usions-The EETs thus formed will be released and activate K+ channels,
increase outward K+ current, and hyperpolarize the plasma membrane. T
he resulting membrane hyperpolarization inhibits voltage-gated Ca2+ ch
annels and leads to arteriolar dilation, thereby increasing regional n
utritive blood now in response to neuronal activity.