The allocentric place discrimination task is selectively and highly dependent on the central muscarinic system in rats

The allocentric place discrimination task (APDT) is useful in evaluating wo rking memory separately from and simultaneously with motivation, motor and sensory ability. Muscarinic acetylcholine receptor antagonist scopolamine h as been shown to selectively impair the accuracy of APDT without changing s wimming speed, distance, and still time. For further evaluation of other ne urotransmitters' roles in the APDT, pharmacological manipulations were perf ormed. Neither diazepam 3.0 mg/kg, mecamylamine 10 mg/kg, haloperidol 0.5 m g/kg, nor 8-OH DPAT 1.0 mg/kg affected accuracy of place discrimination. Tw o kinds of responses were observed following the administration of MK-801 0 .3 mg/kg: the accuracy of rats for longer swimming distance tended to decre ase, and the accuracy of rats for normal swimming distance did not change. Therefore, NM-801 did not seem to affect the working memory selectively. In addition, neither flumazenil 10 mg/kg, ondansetron 0.3 mg/kg nor R(-)-alph a-metylhistamine 10 mg/kg attenuated the scopolamine-induced deficits. Thes e results suggest that the central muscarinic receptors are selectively and highly important in the APDT. (C) 1999 Elsevier Science Inc.