Release of adenosine 5′-triphosphate from synaptosomes from different regions of rat brain

The release of adenosine 5′-triphosphate by elevated extracellular concentrations of KC1 and by veratridine was determined in synaptosomal fractions prepared from different regions of rat brain. Following correction for yields of synaptosomes from the various regions, the relative distribution of K⁺-induced release was corpus striatum > cerebral cortex > medulla > hypothalamus > cerebellum. In contrast, the relative distribution of veratridine-induced release of adenosine 5′-triphosphate was medulla > corpus striatum > hypothalamus > cerebral cortex > cerebellum. From these findings, it was concluded that (1) depolarization-induced release of adenosine 5′-triphosphate was not distributed uniformly throughout the brain but varied from region to region, (2) the K⁺-induced release of adenosine 5′-triphosphate which is Ca²⁺-dependent, had a different regional distribution than the veratridine-induced release, which is greatest in Ca²⁺-free medium, and (3) the distribution of K⁺-induced release of adenosiae 5′-triphosphate did not correlate well with the known distribution of noradrenaline concentrations in rat brain, but did correlate to some extent with the distributions of 5-hydroxytryptamine, dopamine and especially acetylcholine, so that co-release of adenosine 5′-triphosphate with these transmitters may possibly occur.