title: Time-Specific Fear Acts as a Non-Photic Entraining Stimulus of Circadian Rhythms in Rats.
abstract: Virtually all animals have endogenous clock mechanisms that "entrain" to the light-dark (LD) cycle and synchronize psychophysiological functions to optimal times for exploring resources and avoiding dangers in the environment. Such circadian rhythms are vital to human mental health, but it is unknown whether circadian rhythms "entrained" to the LD cycle can be overridden by entrainment to daily recurring threats. We show that unsignaled nocturnal footshock caused rats living in an "ethological" apparatus to switch their natural foraging behavior from the dark to the light phase and that this switch was maintained as a free-running circadian rhythm upon removal of light cues and footshocks. Furthermore, this fear-entrained circadian behavior was dependent on an intact amygdala and suprachiasmatic nucleus. Thus, time-specific fear can act as a non-photic entraining stimulus for the circadian system, and limbic centers encoding aversive information are likely part of the circadian oscillator network that temporally organizes behavior.
authors.affiliation: Department of Psychology, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Blake A
authors.initials: BA
authors.lastname: Pellman
authors.affiliation: Department of Psychology, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Earnest
authors.initials: E
authors.lastname: Kim
authors.affiliation: Department of Psychology, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Melissa
authors.initials: M
authors.lastname: Reilly
authors.affiliation: Department of Psychology, University of Washington, Seattle, Washington 98195, USA.
authors.forename: James
authors.initials: J
authors.lastname: Kashima
authors.affiliation: Department of Psychology, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Oleksiy
authors.initials: O
authors.lastname: Motch
authors.affiliation: Department of Biology, University of Washington, Seattle, Washington 98195, USA.|Program in Neuroscience, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Horacio O
authors.initials: HO
authors.lastname: de la Iglesia
authors.affiliation: Department of Psychology, University of Washington, Seattle, Washington 98195, USA.|Program in Neuroscience, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Jeansok J
authors.initials: JJ
authors.lastname: Kim
mesh_terms: D000679:Amygdala / Q000502:physiology; D000818:Animals; D001522:Behavior, Animal; D002940:Circadian Rhythm; D003463:Cues; D005239:Fear; D005247:Feeding Behavior; D017440:Photoperiod; D010812:Physical Stimulation; D051381:Rats; D013493:Suprachiasmatic Nucleus / Q000473:pathology / Q000502:physiology