Pharmacological Resetting of the Circadian Sleep-Wake Cycle Effects of Triazolam on Reentrainment of Circadian Rhythms in a Diurnal Primate

An attempt was made to accelerate the reentrainment of circadian rhythms in squirrel monkeys exposed to 8-hr phase advances and phase delays of the daily light-dark cycle by timed administration of the short-acting benzodiazepine, triazolam. On the day of the phase advance, each animal received a single injection of triazolam 0.3 mg or of vehicle alone in mid-subjective day, 2 hr after the new time of dark onset, while on the day of the phase delay, the animals received triazolam or vehicle in late subjective night, just before dark onset. The daily acrophases of the circadian rhythm of body temperature were calculated by cosinor analysis, and exponential functions were fitted to the acrophases that followed each of the phase shifts. The rates of reentrainment, defined as the time required for the exponential functions to reach 90 of their asymptotic values, were slower after the phase advance than after the phase delay but did not differ significantly between drug and vehicle conditions. Keywords Circadian rhythms, Entrainment, Body Temperature, Phase shift, Benzodiazepines, Triazolam.