Hypothalamic control of feeding behavior in the thirteen-lined ground squirrel
Abstract
The thirteen-lined ground squirrel (Ictidomys tridecemlineatus) undergoes natural,
extreme changes in feeding behavior, including a six-month fast during hibernation. In
the spring and summer, ground squirrels become hyperphagic by increasing food intake
for fat storage during hibernation. Immediately before hibernation, they decrease food
intake and become hypophagic. The reverse process occurs after hibernation. mRNA
expression in the hypothalamus of the brain during the fall feeding transition in the
ground squirrel showed increased orexigenic expression during hyperphagia and
decreased expression during hypophagia (Schwartz, Hampton, & Andrews, 2015).
However, protein expression is not known. Orexigenic protein expression of mRNA
targets that are interesting to human health include neuropeptide Y (NPY) and orexin A.
We used immunohistochemistry to detect NPY and orexin A protein expression levels
over hyperphagic, fall hypophagic, interbout arousal (during hibernation), and spring
hypophagic transitions. c-fos, a marker for neuronal activity, was used to determine
active areas of the hypothalamus during feeding transitions. Coverage and cell count
revealed increased NPY and orexin A expression during periods of hyperphagia and
complementary to this, increased c-fos expression in lateral hypothalamic neurons during
hyperphagia. This suggested that orexin A is a key player in feeding control of the ground
squirrel, particularly during hyperphagia.
Subject
Biology
Ground squirrels -- Hibernation
Hyperphagia