The cognitive effect profiles of NMDA receptor modulating drugs are resolvable if stimulus complexity is varied in a...

Number discernment is at the heart of task accuracy for laboratory animals performing Fixed Consecutive Number (FCN) operant tasks. Narrow-limit FCN tasks, in particular, are useful for measuring working memory in rat subjects because performance efficacy, which is set up to concord with food delivery, depends on a fairly precise quantification of cues generated by the rat's ongoing behavior. Reported here is a behavioral pharmacology study that utilized a group of overtrained and FCN-schedule-compliant rats injected in a randomized series of testing sessions with different types of N-methyl-D-aspartate (NMDA) receptor modulating drugs. Modifications made to the narrow-limit FCN schedule permitted a simultaneous measure of drug-induced compromises in subjects' sensory integrative or motor coordinating capabilities. This highly sensitive model implicated the intrachannel and the glutamate recognition NMDA receptor binding sites as prime mediators of NMDA antagonist associated memory impairments because drugs acting at the mentioned sites lowered counting efficacy without altering sensorimotor function.