Stimulating effect of methylmercury chloride on [(3)H]acetylcholine release from guinea-pig striatal slices.

The effect of methylmercury (MeHg) chloride on the release of [(3)H]acetylcholine ([(3)H]ACh) was examined using guinea-pig striatal slices. When the Hg concentration in the striatal slices was less than 10 ppm, MeHg chloride had no effect on spontaneous [(3)H]ACh release. However, electrically evoked release of [(3)H]ACh was significantly increased when the tissue Hg concentration was between 0.08 and 3 ppm and was about 160% of the control value at around 0.7 ppm. The increase in evoked ACh release induced by MeHg chloride at low tissue concentrations was partly due to inhibition of the re-uptake of choline. These results suggest that MeHg chloride-induced hyperactivation of cholinergic transmission may be involved in some of the early signs of mercury intoxication.