CIRCANNUAL CONTROL OF HIBERNATION AND
SEASONAL AFFECTIVE DISORDER
Some
animals show a special physiological adaptation for surviving the cold
temperatures and reduced food availability during winter season, consisting in
a dramatic drop in body temperature, until 5°C, and an associated depression in
metabolic activity and circulation. This unique physiological feat, known under
the name of hibernation, seems to be controlled by a hibernation specific
protein (HP) complex.
Kondo
and colleagues, who previously identified HP, have now discovered that brain
level of the HP20c subunit increases during hibernation (Circannual control of
hibernation by HP complex in the brain. Cell 125, 161-172, 2006).
The
research shows that HP20c levels were not altered as a result of factors such
as temperature changes, but instead were altered by endogenous circannual
control.
Does
HP20c control hibernation?
To
answer the question Kondo and his colleagues blocked the subunit action using
an anti-HP20c-Ab. As a result they found a significantly shorter hibernation
time.
A
role for HP20c is also evident in particular chipmunks unable to generate
increased levels of HP20c; indeed, these animals were also unable to initiate
hibernation in the winter season.
Taken
together these findings indicate HP20c as a factor in controlling this special
annual adaptation. Discovering molecular bases of circannual control could help
understanding human circannual recurrence of seasonal affective disorder.