An in vivo cholinergic influence on the retention of [3H]noradrenaline in regional brain synaptosomes.

Rats were intraventricularly (icv) injected with [3H]noradrenaline and the retention of the amine was determined in synaptosomes obtained from cerebral cortex, hypothalamus and brain stem. Previous icv administration of hemicholinium-3, effective enough to markedly decrease brain acetylcholine levels, increased the retention of synaptosomal [3H]noradrenaline in hypothalamus and cerebral cortex; this increased retention did not occur in the brain stem. The increased retention of [3H]noradrenaline, produced by hemicholinium-3, was reversed by a concomitant icv dose of choline, which in turn reversed the decrease of acetylcholine caused by hemicholinium-3. These results are interpreted as brain cholinergic activity having an influence on the turnover of noradrenaline in some brain regions.