AJP - Regulatory, Integrative and Comparative Physiology, Vol 238, Issue 5 318-R327, Copyright © 1980 by American Physiological Society
Blood-brain barrier transport and cerebral utilization of dopa in living monkeys
E. S. Garnett, G. Firnau, C. Nahmias, S. Sood and L. Belbeck
[18F]fluoro-dopa, DL-3,4-dihydroxy-5-[18F]fluorophenylalanine, a tracer for
dopa, was injected intravenously into cynomolgus monkeys anesthetized with
enflurane, and the appearance of 18F in the head and the disappearance of
18F from the blood were each measured continuously for 10 min with simple
gamma-ray detectors. A three-compartment explanatory model was used to
derive fractional rate constants for the forward flux of L-dopa into the
endothelium of the brain capillaries from the blood (1.54 +/- 0.37 min-1),
the back flux of dopa and/or its metabolites to the blood from the
endothelium (0.67 +/- 0.05 min-1), the formation of dopamine from dopa
(0.20 +/- 0.04 min-1), and the destruction of dopamine (0.04 +/- 0.02
min-1). It was also shown that only one-fifth of the dopa that entered the
endothelium was available for dopamine synthesis in neurons. It was
concluded that the technique described could be extended to man and used to
investigate the role of dopa and dopamine in the control of mood and
locomotion.
