Effect of prolonged administration of nitrazepam on sleep cycles in rats

The effect of nitrazepam given as a single dose or by prolonged intraperitoneal injection, on sleep cycles in male Wistar rats was studied. In a dose of 1 mg/kg nitrazepam had no significant effect on sleep cycles whether given as a single or by prolonged injection. In a dose of 10 mg/kg a single injection of nitrazepam reduced the duration of paradoxical sleep and the number of sleep cycles during 5 h of recording, whereas prolonged (7–14 days) administration of the drug led to an increase in these indices. Withholding the drug after its prolonged administration was followed by a further increase in the number of sleep cycles and the duration of paradoxical sleep. No correlation was found between the hypnotic and muscle-relaxing action of nitrazepam during its prolonged administration.Institute of Pharmacology, Academy of Medical Sciences of the USSR, Moscow. Institute of Pharmacology, Czechoslovak Academy of Sciences, Prague. (Presented by Academician of the Academy of Medical Sciences of the USSR V. V. Zakusov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 81, No. 2, pp. 188–190, February, 1976.