Cholinergic-glutamatergic interactions in visual recognition memory of rhesus monkeys

Administration of either a non-competitive N-methyl-D-aspartatc (NMDA) receptor antagonist, MK-801 (dizocilpine), or a muscarmic antagonist, scopolamine, produces dose-related impairments in performance of a visual recognition memory task, delayed non-matching to sample (DNMS) with lists of 20 symbols, in rhesus monkeys. In the present study, low doses of these two drugs, which were ineffective when given alone, significantly impaired performance when given in combination. Moreover, the effect was greater than additive, indicating a synergistic interaction. These results suggest that interactions between cholincrgic and glutamatergic systems play an important role in regulation of visual recognition memory.