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circadian disruptions, and that both physiological and circadian symptoms
can be ameliorated with timed administration of bright light and/or mela-
induce psychotic or major affective disorders, circadian disruption in
humans can lead to relapse of symptoms in people with a history of psychi-
alignment
in humans correlates with the severity of
symptoms
in
4.6.1 Environmental models
Seasonal depression is associated with changes in circadian function caused
by alterations in light exposure, and experimental work has focused on the
nature of this relationship. Entrainment to short photoperiods and decreased
light exposure is associated with depression in diurnal rodents,
340-343
whether day length influences affective responses of nocturnal rodents can
be markedly influenced by species, strain, type of behavioral test employed,
changes in affective state in nocturnal rodents, with mice held under constant
light displaying behavioral measures of depression and decreased anxiety.
348
Moreover, anxious- and depressive-like behavior is evident in mice exposed
Under free-running conditions with aberrant light at night, depression-like
behavior can be ameliorated with fluoxetine administration or ablation of
intrinsically photosensitive melanopsin-containing retinal ganglion cells.
56
Lastly, mice exposed to non-24 h LD cycles (20 h) display an increased
impulsivity phenotype when tested under novel environmental condi-
exposed to a weekly 6 h LD shift.
353
4.6.2 Genetic models
Clock gene expression rhythms are evident in a variety of structures impor-
between clock gene function and mood is provided by studies conducted
with the
clock
mutant mouse, which has been proposed as a model for mania
due to its hyperactivity, decreased depressive- and anxiety-like behavior,
to the face validity of the
clock
mutant model for mania, this behavioral
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