Effects of T-82, a new quinoline derivative, on cholinesterase activity and extracellular acetylcholine concentration in rat brain

The effects of T-82 (2-[2-(1-benzylpiperidin-4-yl)ethyl]-2,3-dihydro-9-methoxy-1H-pyrrolo [3,4-b]quinolin-1-one hemifumarate), a new quinoline derivative, on acetylcholinesterase (AChE) activity and acetylcholine (ACh) release were compared with those of the well-known cholinesterase inhibitors tacrine and E2020. T-82, tacrine and E2020 all concentration-dependently inhibited AChE in rat brain homogenate (IC50 = 109.4, 84.2 and 11.8 nM, respectively). In addition, although tacrine strongly inhibited butyrylcholinesterase (BuChE), T-82 and E2020 showed only weak activity on BuChE in human plasma. In ex vivo experiments, intraperitoneal administration of T-82 at a dose of 30 mg/kg inhibited AChE activity in the hippocampus, frontal cortex and parietal cortex of rats. The effect of T-82 on the extracellular ACh concentration in rat brain was measured using in vivo microdialysis. T-82 at doses of 10 and 30 mg/kg, i.p. increased the extracellular ACh concentration in the hippocampus and striatum in a dose-dependent manner. These findings suggest that T-82 activates the central cholinergic system by selectively inhibiting AChE activity, while weakly affecting peripheral BuChE activity, and that T-82 increases the extracellular ACh concentration in the brain, which is followed by inhibited AChE activity.