Alterations in synaptosomal calcium concentrations after rapid eye movement sleep deprivation in rats

Rapid eye movement sleep deprivation alters behavioral and physiological, as well as cellular functioning and responsiveness. Since intracellular calcium concentration plays an important role in regulating cellular functions, it was hypothesized that such deprivation might induce changes in intracellular calcium concentration. Therefore, in this study, rats were deprived of rapid eye movement sleep by the flower-pot technique, and total, bound and free calcium concentrations were estimated in synaptosomal preparations from the cerebrum, cerebellum, brainstem, midbrain, pons and medulla. Rapid eye movement sleep deprivation was continued for two or four days and suitable control experiments were conducted to rule out the effects of non-specific factors. Total calcium concentration increased in the brainstem but showed a decrease in the cerebellum and cerebrum. After four days deprivation, the free calcium concentration always decreased; however, the bound calcium concentration decreased in the cerebrum and cerebellum but increased in the brainstem. After two days' deprivation, the medulla was the only region where the bound calcium increased while the free form decreased; only the free form decreased in the pons, while the midbrain was never affected. The results suggest that there was a net efflux of calcium in the cerebellum and cerebrum, but a net influx in the brainstem. The findings support our hypothesis and help to explain earlier observations. Since it is known that calcium plays an important role in cellular functioning, these changes in calcium concentration may be the underlying mechanism for rapid eye movement sleep deprivation-induced cellular expressions and behavior of neurons.