Absence of amnesia induction in mice with hydroxyzine in comparison with three other minor tranquillizers

Hydroxyzine (Atarax) was compared with three traditional anxiolytics (diazepam, meprobamate, triazolam) for potential amnesic activity in a step-through passive avoidance task in the mouse. The doses investigated were: hydroxyzine (4, 8 and 16 mg/kg); diazepam (0.25, 0.5 and 1 mg/kg); meprobamate (8, 16 and 32 mg/kg); triazolam (0.0015, 0.003 and 0.006 mg/kg). The doses investigated were chosen on the basis of prior experiments for not having sedative effects as measured in a photo-cell activity meter. All drugs were administered i.p. 30 min before the first trial of the passive avoidance task. The compounds were also investigated for eventual analgesic activity using the hot plate test. The results indicated that hydroxyzine up to sedative doses was devoid of amnesic activity, whereas clear signs of amnesia were induced by diazepam, meprobamate and triazolam at doses at least 8 times lower than those which reduced spontaneous motor activity. None of the compounds showed analgesic activity in the hot plate test suggesting that the signs of amnesia observed in the passive avoidance test were not due to reduced sensitivity to aversive stimulation.