62ª Reunião Anual da SBPC

C. Ciências Biológicas - 12. Neurociências e Comportamento - 1. Neurociências e Comportamento

EXPERIENCE-DEPENDENT ACTIVATION OF CaMKII AND MAPK IN THE RAT HIPPOCAMPUS DURING SLEEP

Cátia Mendes Pereira 1 Vinícius Rosa Cota 1, 3 Sharlene Santos 2, 1 Annie da Costa Souza 1, 2 Gabriela Dias 1, 2 Sidarta Ribeiro 1, 2

1. Edmond and Lily Safra International Institute of Neuroscience of Natal(ELS-IINN) 2. Federal University of Rio Grande do Norte (UFRN), Natal/RN - Brazil 3. Federal University of São João Del-Rei (UFSJ), São João Del-Rei/MG - Brazil

INTRODUÇÃO:

Sleep-dependent plastic changes play a key role in the consolidation of newly acquired memories. Two distinct and successive phases of sleep, slow wave sleep (SWS), and rapid eye movement (REM) sleep can be recognized in mammals. Both phases have been implicated in the sensorimotor processing of daytime events, but the molecular mechanisms involved remain poorly understood. Brain expression of the plasticity-associated immediate-early gene (IEG) zif-268 is upregulated during REM sleep in the cerebral cortex and hippocampus of animals exposed to rich sensorimotor experience in the preceding waking period (Ribeiro et al., Learn Mem. 6; 500, 1999). Zif-268 integrates a major calcium signal transduction pathway which includes Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and mitogen activated protein kinase (MAPK). CaMKII autophosphorylation of T286 provides a biochemical memory that is critical for plasticity, and MAPK has been implicated in hippocampal long-term potentiation (LTP) and learning and memory in behaving animals. Our goal here is to investigate the phosphorylation levels of CaMKII and MAPK during sleep in rats exposed to a new rich environment in the preceding waking period.

METODOLOGIA:

Intracranial local field potentials (LFPs) recorded in the cortex and hippocampus were used to characterize the wake-sleep cycle. After the recovering surgery period (three days minimum) adult Wistar rats (n=30) were handled and habituated to the experiment box over the three preceding days of the experiment. In our experimental setup animals were exposed to four new objects for sensorimotor stimulation during ten minutes, and were then sleep deprived for the next three hours. After deprivation the animals were allowed to sleep (except the waking group) until they reached a target sleep phase (SWS or REM). Once a criterion time of sleep was achieved, animals were sacrificed. The cerebral hemispheres were dissected for western blotting. The phosphorylation levels of CaMKII, MAPK and PKC were assessed using specific antibodies.

RESULTADOS:

Our data indicate that the CaMKII and MAPK pathways were significantly activated in awake rats and downregulated during sleep. Controls unexposed to novel experience did not show kinase activation in the waking period. Contradictory results in the sleep literature regarding synaptic upscaling or downscaling are likely related to the use of different methods, biased towards global (e. g. western blots) versus local (e. g. in situ measurements) effects.

CONCLUSÃO:

Our results indicate that sleep harbors mechanisms of synaptic downscaling. We have previously proposed that REM sleep triggers synaptic upscaling within circuits selected by waking experience, while the remaining circuits undergo synaptic downscaling. Preliminary in situ measurements (immunohistochemistry) support this hypothesis.

Instituição de Fomento: AASDAP, CNPq, FINEP, FAPERN

Palavras-chave: Sleep, Memory, Hippocampus.