The Journal of Neuroscience, June 15, 2000, 20(12):4669-4679
c-Fos Expression in GABAergic, Serotonergic, and Other
Neurons of the Pontomedullary Reticular Formation and Raphe after
Paradoxical Sleep Deprivation and Recovery
Karen J.
Maloney,
Lynda
Mainville, and
Barbara E.
Jones
Department of Neurology and Neurosurgery, McGill University,
Montreal Neurological Institute, Montreal, Quebec H3A 2B4, Canada
The brainstem contains the neural systems that are necessary for
the generation of the state of paradoxical sleep (PS) and accompanying
muscle atonia. Important for its initiation are the pontomesencephalic
cholinergic neurons that project into the pontomedullary reticular
formation and that we have recently shown increase c-Fos expression as
a reflection of neural activity in association with PS rebound after
deprivation in rats (Maloney et al., 1999). As a continuation, we
examined in the present study c-Fos expression in the pontomedullary
reticular and raphe neurons, including importantly GABAergic neurons
[immunostained for glutamic acid decarboxylase (GAD)] and
serotonergic neurons [immunostained for serotonin (Ser)].
Numbers of single-labeled c-Fos+ neurons were significantly increased
with PS rebound only in the pars oralis of the pontine reticular nuclei
(PnO), where numbers of GAD+/c-Fos+ neurons were conversely
significantly decreased. c-Fos+ neurons were positively correlated with
PS, whereas GAD+/c-Fos+ neurons were negatively correlated with PS,
suggesting that disinhibition of reticular neurons in the PnO from
locally projecting GABAergic neurons may be important in the generation
of PS. In contrast, through the caudal pons and medulla, GAD+/c-Fos+
cells were increased with PS rebound, covaried positively with PS and
negatively with the electromyogram (EMG). In the raphe
pallidus-obscurus, Ser+/c-Fos+ neurons were positively correlated, in a
reciprocal manner to GAD+/c-Fos+ cells, with EMG, suggesting that
disfacilitation by removal of a serotonergic influence and inhibition
by imposition of a GABAergic influence within the lower brainstem and
spinal cord may be important in the development of muscle atonia
accompanying PS.
Key words:
paradoxical sleep; REM sleep; c-Fos expression; reticular
formation; raphe; GABAergic; serotonergic; sleep-wake states; muscle
atonia
Copyright © 2000 Society for Neuroscience 0270-6474/00/20124669-11$05.00/0