Arecoline via Miniosmotic Pump Improves AF64A-Impaired Radial Maze Performance in Rats: A Possible Model of Alzheimer's Disease

Male Sprague–Dawley rats, preoperatively trained in a 1-h delay non-match-to-position radial maze task, received bilateral stereotaxic injections of a selective cholinotoxin, ethylcholine aziridinium ion (AF64A: 3 nmol/3 μl/lateral ventricle). Animals treated with AF64A made significantly more total postdelay errors than vehicle controls. Sustained delivery, via miniosmotic pumps, of arecoline (0.1, 0.3, 1, 3, 10, or 30 mg/kg/day sc for 14 days) attenuated the AF64A-induced cognitive impairment in a dose-dependent manner, producing an inverted U-shaped dose–response function which was optimal at 1.0 mg/kg/day. Following these studies, choline acetyltransferase activity was significantly reduced in hippocampi extracted from the AF64A-treated rats, indicating successful cholinotoxicity. This paradigm may be useful as a possible screen for potential Alzheimer's disease therapeutic agents. This conclusion is supported by published reports of beneficial arecoline effects observed following 2-week intravenous infusions in patients with Alzheimer's disease (Soncrant, Raffaele, Asthana, Berardi, Morris, & Haxby, 1993).