Dopamine release induced by electrical stimulation of microdissected caudate-putamen and substantia nigra of the rat brain

Dopamine release was induced by electrical stimulation of minute samples from rat caudate putamen and substantia nigra (approximately 3 mg of wet tissue). The characteristics of the superfusion chamber and stimulation device are described. The stimulation consisted of rectangular and biphasic pulses at 50 Hz applied for 15 seconds. The apparent threshold to induce measurable release was 2 mA. Supramaximal stimulation was obtained at 8–10 mA. The release from both caudate putamen and substantia nigra was found to be calcium-dependent and tetrodotoxin-sensitive. 4-aminopyridine, an agent known to prolong the duration of action potential, potentiated the electrically-induced release of dopamine from caudate putamen samples. This strongly suggests that the electrically-induced release was evoked by action potentials generated in dopaminergic fibres of the caudate putamen.We conclude that the procedure here described makes it possible to study the release of putative transmitters from individual isolated, microdissected, nuclei from the central nervous system.