Changes in rat striatum catecholamine during hypoxia with reference to protective effects of flunarizine

We investigated the changes in dopamine, homovanillic acid, 3,4-dihydroxyphenylacetic acid, and norepinephrine content in striatum of rats ventilated with 5% oxygen in nitrogen gas. We also examined the effects of flunarizine, a calcium channel blocker, on these catecholamine levels. During 10-20 min. of hypoxia, the dopamine content gradually increased and the 3,4-dihydroxyphenylacetic acid and norepinephrine levels decreased, while the concentration of homovanillic acid remained unchanged. The concentrations of these substances subsequently returned to control values after 4 hr of room air breathing. In animals pretreated with intravenous flunarizine injection, there was a slight increase in dopamine, with no appreciable change in homovanillic acid or 3,4-dihydroxyphenylacetic acid content during 10-20 min. of hypoxia. The decrease in norepinephrine which occurred during 10-20 min. of hypoxia was identical between non-treated and flunarizine-treated animals. Catecholamine levels subsequently returned to control values after 4 hr of room air breathing. These results suggest that flunarizine minimizes the alterations in striatal catecholamine contents during hypoxic ventilation.