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.