Dopamine-acetylcholine interaction in the striatum studied by microdialysis in the awake rat: some methodological aspects.

In order to evaluate the dopamine/acetylcholine balance hypothesis, sulpiride, (-)-N-0437, oxotremorine or physostigmine were administered intraperitoneally to rats, whereas the extracellular levels of acetylcholine and dopamine in the striatum were recorded by microdialysis. The changes in dialysate concentration of the transmitters did not support the supposed interaction between dopaminergic and cholinergic neurons. Next, we infused direct and indirect dopamine agonists such as (-)-N-0437, amphetamine and nomifensine via the dialysis membrane. The dopamine agonists had no effect on the release of acetylcholine when the calcium concentration of the perfusion fluid was 3.4 mmol/l, but the agonists effectively inhibited the release of the transmitter when the calcium concentration was 1.2 mmol/l. The cholinergic drugs physostigmine, oxotremorine, atropine did not affect the release of dopamine.