Basal acetylcholine release in freely moving rats detected by on-line trans-striatal dialysis: pharmacological aspects.

The basal release of acetylcholine (without the use of an esterase inhibitor) from brain tissue was quantified by means of transversal striatal dialysis in freely moving rats, coupled on-line to an HPLC analysis system. Basal release of acetylcholine was shown to be fully calcium dependent and tetrodotoxin sensitive. A comparison between a U-shaped and a transversally localized dialysis probe was made and some important differences were noticed. The use of a transversal probe resulted in a 20 times higher recovery when compared with the U-shaped cannula. The effect of the cholinomimetic oxotremorine and the anticholinergic atropine on the basal acetylcholine output was determined. Atropine increased the output of acetylcholine, whereas oxotremorine induced a decrease in the output of the transmitter. Application of various degrees of esterase inhibition (by addition of neostigmine to the perfusion fluid) did not qualitatively interfere with the effects of oxotremorine or atropine on the release of acetylcholine.