Distribution of Hypocretin-Containing Neurons in the Lateral Hypothalamus and c-Fos-Immunoreactive Neurons in the VLPO
Dean Wagner, Rafael Salin-Pascual, Mary Ann Greco and Priyattam J. Shiromani
West Roxbury VA Medical Center and Harvard Medical School, West Roxbury, MA
ABSTRACT
The present study investigated the distribution
of neurons implicated in the regulation of sleep in
three species generally used in sleep research,
i.e., mice, rats and cats. We focused on sleep
active neurons in the ventral lateral preoptic
(VLPO) area and the
hypocretin/orexin-containing neurons in the
lateral hypothalamus. The latter groups of
neurons were found recently to play an
important role in the regulation of REM sleep.
The expression of the transcription factor,
c-Fos, was used to identify the VLPO. In mice
and rats, in response to sleep, a discrete cluster
of c-Fos positive cells was found in the VLPO. In
mice, this cluster was located more medially
compared to the rat, and as in the rat, galanin
immunostained neurons were found in the VLPO.
In the cat, c-Fos positive cells did not segregate
to a specific location but were more diffusely
represented in the preoptic area. In all three
species, orexin/hypocretin-containing neurons
were located only in the lateral hypothalamus
with the distribution being more diffuse in the
cat. The grouping of sleep-active cells in rodents
makes it feasible to extract these cells for tissue
culture and molecular analysis. Moreover, given
that rodents have a distinct circadian distribution
of sleep-wakefulness, the connectivity with the
suprachiasmatic nucleus can also be determined.