BRAIN INCORPORATION OF [1-C-11]ARACHIDONATE IN NORMOCAPNIC AND HYPERCAPNIC MONKEYS, MEASURED WITH POSITRON EMISSION TOMOGRAPHY

Positron emission tomography (PET) was used to determine brain incorpo ration coefficients k of [1-C-11]arachidonate in isoflurane-anestheti zed rhesus monkeys, as well as cerebral blood flow (CBF) using [O-15]w ater. Intravenously injected [1-C-11]arachidonate disappeared from pla sma with a half-life of 1.1 min, whereas brain radioactivity reached a steady-state by 10 min. Mean values of k were the same whether calcu lated by a single-time point method at 20 min after injection began, o r by least-squares fitting of an equation for total brain radioactivit y to data at all time points. k equalled 1.1-1.2 X 10(-4) ml.s(-1).g( -1) in gray matter and was unaffected by a 2.6-fold increase in CBF ca used by hypercapnia. These results indicate that brain incorporation o f [1-C-11]arachidonate can be quantified in the primate using PET, and that incorporation is flow-independent.