MKC-231, a choline uptake enhancer: (2) Effect on synthesis and release of acetylcholine in AF64A-treated rats

The effect of MKC-231 on acetylcholine (ACh) synthesis and release was studied in the hippocampus of normal and AF64A-treated rats. AF64A (3 nmol/brain, i.c.v.) produced significant reduction of high-affinity choline uptake (HACU) and high K(+)-induced ACh release in hippocampal synaptosomes. Treatments with MKC-231 (10(-8) and 10(-7) M) showed significant reverse of the decrease in both HACU and ACh release. In hippocampal slices superfused with choline-containing artificial cerebrospinal fluid (ACSF), high K(+)-induced ACh release was gradually decreased by repeated alteration of resting and high K(+) stimulations in AF64A-treated rats. However, addition of MKC-231 (10(-8) to 10(-7) M) in the superfusate reduces this decrease. In vivo microdialysis studies indicate MKC-231 (10 mg/kg, p. o.) significantly reversed reduction of basal ACh concentrations in AF64A-treated rats, measured by radioimmunoassay without a cholinesterase inhibitor in the perfusate. These results indicate MKC-231 improves AF64A-induced cholinergic hypofunction by enhancing HACU, subsequently facilitating ACh synthesis and release in vitro and in vivo.