M. Yonetani et al., EFFECT OF ACUTE COCAINE INJECTION ON THE EXTRACELLULAR LEVEL OF DOPAMINE, BLOOD-FLOW, AND OXYGEN-PRESSURE IN BRAIN OF NEWBORN PIGLETS, Biochemical medicine and metabolic biology, 51(1), 1994, pp. 91-97
The present study examined the effects of acute cocaine administration
on oxygen pressure in the vasculature of the cortex as well as on blo
od dow and extracellular levels of dopamine in the striatum of newborn
piglets. The oxygen dependent quenching of phosphorescence was used t
o continuously monitor oxygen pressure in the vasculature of the corte
x. Following acute cocaine injection (1.5 mg/kg iv) the cortical oxyge
n pressure rapidly decreased from 36.3 +/- 1.2 to 32.9 +/- 1.4 Torr an
d remained at the lower level during the 120 min of postinjection peri
od during which measurements were made. Blood dow in striatum, as dete
rmined by laser Doppler, was decreased by 8-10% at 5 min after injecti
on of cocaine. This decrease in blood flow was statistically significa
nt up to 40 min postinjection. Extracellular dopamine, measured using
in vivo micro dialysis, showed a large increase after cocaine injectio
n. The dopamine level increased from 14 +/- 7 to 88 +/- 21 pmol/ml by
15 min after drug administration, then decreased to 45 +/- 11 pmol/ml
and remained stable for the 120 min post-injection period. The mechani
sm(s) by which the increase in the extracellular level of dopamine occ
urred may include a direct effect of cocaine on the dopamine transport
er and/or an indirect effect due to the decrease in cerebral oxygenati
on and blood flow. The increase in extracellular dopamine can be respo
nsible for several alterations in neuronal metabolism with potentially
deleterious effects on neuronal function. (C) 1994 Academic Press, In
c.