[Abstract Title]. - Society for Neuroscience

HL60296
MH63323
Title: Sleep-related c-Fos expression in neurons projecting from preoptic hypothalamus to
periaqueductal gray
Authors: *J.-C. HSIEH 1,3 , A. USCHAKOV 1,3 , D. MCGINTY 2 , R. SZYMUSIAK 1,3 ;
1 Med., 2 Psychology, UCLA, North Hills, CA; 3 Res. Service, V. A. Greater Los Angeles
Heathcare Syst., North Hills, CA
Abstract: The midbrain periaqueductal gray (PAG) is involved various physiological functions
including autonomic regulation and sleep-wake control. The preoptic hypothalamus is an
important source of afferents to the PAG. The preoptic area also contains populations of putative
sleep-regulatory neurons that are activated during sleep. To investigate the extent to which
preoptic-PAG projection neurons are sleep-active, we combined retrograde tracer injection into
the PAG with c-Fos protein immunostaining in the preoptic area.
Adult male Sprague-Dawley rats (n=6) were used in this study. Retrograde tracer, Fluoro-gold
(FG), was pressure-injected into the PAG with a Hamilton microsyringe controlled by an
infusion pump. Cortical EEGs and nuchal EMG electrodes were also implanted at the time of
tracer injection. The animals were allowed to recover from surgery and entrained to a 12/12
light/dark cycle. Nine days after tracer injection, the animals were subjected to 2-hours of sleep
deprivation by gentle handling, starting at the onset of light period. This was followed by a 2hour
undisturbed recovery period. Animals were then promptly anesthetized at the end of
recovery period and perfused transcardially with saline followed by paraformaldehyde. The
brains were sectioned and processed for c-Fos protein immunohistochemistry. Cells labeled with
c-Fos and FG were mapped and quantified.
In two of 6 animals, injection sites were centered in the ventrolateral PAG, while in the other 4
animals, the injection was centered at the lateral PAG and extended over most of the dorsal to
ventral aspects ipsilateral PAG. Similar and consistent retrograde labeling was found in the
rostral hypothalamus in all animals, with highest amount of labeling in the ipsilateral medial
preoptic nucleus (MPO) and the median preoptic nucleus (MnPO). Other regions containing
retrogradely-labeled cells included lateroanterior hypothalamic nucleus, bed nucleus of stria
terminalis, and lateral preoptic area. Among these areas, significant numbers of c-Fos positive,
retrogradely-labeled neurons were found in MnPO and MPO.
In conclusion, we report the existence of sleep-active neurons in the preoptic hypothalamus that
project to the periaqueductal gray. These neurons may play a role in mediating sleep-related
change in cardiovascular responses.
Disclosures: J. Hsieh, None; A. Uschakov, None; D. McGinty, None; R. Szymusiak, None.
Poster