PHARMACOLOGICAL AND GENETIC APPROACHES FOR THE STUDY OF CIRCADIAN-RHYTHMS IN MAMMALS

Two different approaches have been utilized to study the controlling m echanisms that underlie the generation and entrainment of circadian rh ythms in mammals. The use of specific drugs to alter the period and/or the phase of circadian rhythms has provided new insights into both th e pathways by which environmental information reaches the mammalian ci rcadian pacemaker in the suprachiasmatic nuclei (SCN) and the cellular and neurochemical events within the SCN itself which are involved in circadian rhythmicity. A second approach, which seeks to exploit genet ic differences in the properties of the circadian system, holds the pr omise of eventually defining the cellular and molecular events that ar e part of the clock itself, the events that underlie the entrainment o f the circadian dock by environmental factors, and the expression of o vert rhythms driven by the clock. It is anticipated that the pharmacol ogical and genetic approaches to the study of circadian rhythms will c omplement each other as the underlying physiological mechanisms of the circadian clock system become defined. (C) 1995 Academic Press, Inc.