AJP - Regulatory, Integrative and Comparative Physiology, Vol 259, Issue 3 514-R520, Copyright © 1990 by American Physiological Society
Daily injections of triazolam induce long-term changes in hamster circadian period
O. Van Reeth and F. W. Turek
Institute of Interdisciplinary Research in Human and Nuclear Biology, Universite Libre de Bruxelles, Belgium.
Previous experiments in hamsters indicate that daily injections of the
short-acting benzodiazepine, triazolam, can entrain the free-running
circadian activity rhythm to the period of the injections and that, after
discontinuation of triazolam injections, the period of the free-running
activity rhythm remains close to that of the previous injection schedule
for 20-50 cycles. In this paper, we extend these findings and demonstrate
that 1) long-term treatment with triazolam can induce aftereffects on the
period of the circadian clock underlying the activity rhythm that can last
for up to 100 days, 2) triazolam-induced changes in period can lead to a
loss of effect of daily injections of triazolam which can be restored if
the time of injection is altered, and 3) chronic treatment with triazolam
also alters the period of the circadian clock in animals entrained to a
light-dark cycle, and such changes in period alter the phase relationship
between the circadian clock and the entraining light-dark cycle.
