article
Experience-dependent upregulation of multiple plasticity factors in the hippocampus during early REM sleep
Fecha
2015Registro en:
CALAIS, Julien Braga; et al. Experience-dependent upregulation of multiple plasticity factors in the hippocampus during early REM sleep. Neurobiology of Learning and Memory. 2015. Disponível em: .Doi: 10.1016/j.nlm.2015.01.002
1074-7427
Autor
Calais, Julien Braga
Ojopi, Elida Benquique
Morya, Edgard
Sameshima, Koichi
Ribeiro, Sidarta Tollendal Gomes
Resumen
Sleep is beneficial to learning, but the underlying mechanisms remain controversial. The synaptic homeostasis
hypothesis (SHY) proposes that the cognitive function of sleep is related to a generalized rescaling
of synaptic weights to intermediate levels, due to a passive downregulation of plasticity mechanisms. A
competing hypothesis proposes that the active upscaling and downscaling of synaptic weights during
sleep embosses memories in circuits respectively activated or deactivated during prior waking experience,
leading to memory changes beyond rescaling. Both theories have empirical support but the experimental
designs underlying the conflicting studies are not congruent, therefore a consensus is yet to be
reached. To advance this issue, we used real-time PCR and electrophysiological recordings to assess gene
expression related to synaptic plasticity in the hippocampus and primary somatosensory cortex of rats
exposed to novel objects, then kept awake (WK) for 60 min and finally killed after a 30 min period rich
in WK, slow-wave sleep (SWS) or rapid-eye-movement sleep (REM). Animals similarly treated but not
exposed to novel objects were used as controls. We found that the mRNA levels of Arc, Egr1, Fos, Ppp2ca
and Ppp2r2d were significantly increased in the hippocampus of exposed animals allowed to enter REM,
in comparison with control animals. Experience-dependent changes during sleep were not significant in
the hippocampus for Bdnf, Camk4, Creb1, and Nr4a1, and no differences were detected between exposed
and control SWS groups for any of the genes tested. No significant changes in gene expression were
detected in the primary somatosensory cortex during sleep, in contrast with previous studies using
longer post-stimulation intervals (>180 min). The experience-dependent induction of multiple plasticity-related
genes in the hippocampus during early REM adds experimental support to the synaptic
embossing theory.