Affiliation:
1. Department of Zoology, University of Delhi, Delhi 110 007, India
2. Department of Zoology, C. C. S. University, Meerut 250 004, India
Abstract
We investigated the effects of exposure at ecologically relevant levels of dim light at night (dLAN) on sleep and the 24 h hypothalamic expression pattern of genes involved in the circadian timing (
per2, bmal1
,
reverb-β
,
cry1
,
ror-α
,
clock
) and sleep regulatory pathways (cytokines:
tlr4
,
tnf
-
α
,
il-1β
,
nos
; Ca
2+
-dependent pathway:
camk2
,
sik3
,
nr3a
; cholinergic receptor,
achm3
) in diurnal female zebra finches. Birds were exposed to 12 h light (150 lux) coupled with 12 h of absolute darkness or of 5 lux dim light for three weeks. dLAN fragmented the nocturnal sleep in reduced bouts, and caused sleep loss as evidenced by reduced plasma oxalate levels. Under dLAN, the 24 h rhythm of
per2
, but not
bmal1
or
reverb-β
, showed a reduced amplitude and altered peak expression time; however,
clock
,
ror-α
and
cry1
expressions showed an abolition of the 24 h rhythm. Decreased
tlr4
,
il-1β
and
nos
, and the lack of diurnal difference in
achm3
messenger RNA levels suggested an attenuated inhibition of the arousal system (hence, awake state promotion) under dLAN. Similarly, changes in
camk2
,
sik3
and
nr3a
expressions suggested dLAN-effects on Ca
2+
-dependent sleep-inducing pathways. These results demonstrate dLAN-induced negative effects on sleep and associated hypothalamic molecular pathways, and provide insights into health risks of illuminated night exposures to diurnal animals.
Funder
Science and Engineering Research Board
Subject
General Agricultural and Biological Sciences,General Environmental Science,General Immunology and Microbiology,General Biochemistry, Genetics and Molecular Biology,General Medicine
Cited by
18 articles.
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