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The effects of single oral doses of DN-2327 (DN, 2 mg or 3 mg), a newly developed partial benzodiazepine receptor agonist, and alprazolam (APZ, 0.8 mg), a full receptor agonist, on psychomotor function and short-term memory were assessed using three psychometric tests: letter cancellation, visual vigilance and Sternberg's memory scanning task. Twelve healthy male volunteers participated in this study. Randomized, double-blind, cross-over test sessions were conducted at 2-week intervals. Both 3 mg DN and 0.8 mg APZ increased the time to completion of the letter cancellation task at 3 h after administration, but neither had any effect on accuracy of response. In the visual vigilance task, which required relatively intense concentration and continuous attention, both the number of errors and reaction times to correct responses significantly increased from 1.5 to 3.5 h after administration of 3 mg DN and at 3.5 h after administration with 0.8 mg APZ. DN at 2 mg also significantly increased the number of errors from 1.5 to 3.5 h after administration, but it did not affect reaction times. In the memory scanning task, 3 mg DN, but not 2 mg DN or APZ, significantly increased overall reaction times at 2 h after administration. These performance deficits paralleled the time-course changes in serum concentrations of both drugs and appeared to be associated with the hypnotic-sedative effects of the drugs tested. These findings did not support those of previous preclinical studies of DN, indicating superiority of DN over conventional full benzodiazepine agonists/anxiolytics in terms of adverse behavioral consequences.

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