Abstract
In hamsters, the entrance into hibernation is associated with a respiratory acidosis and elevation of the blood plasma concentrations of potassium, calcium, and magnesium. To investigate the effects of presumed hibernation-related ionic changes in the brain interstitium on neuronal function, the transmission properties of hippocampal slices prepared from golden hamsters were studied at low temperature in vitro. Slices were investigated at 15-20°C in artificial cerebrospinal fluid (ACSF) of variable composition (K +, 3-5 m M; Ca 2+, 2-4 m M: Mg 2+, 2-4 m M; pH 7.0-7.7). Population action potentials (population spikes, PS) of CAl pyramidal cells were continuously evoked with 100 μs stimulus pulses delivered to the Schaffer collateral/commissural fibers in intervals of 30 s. The PS amplitude was measured as a function of extracellular ion concentrations at given temperature or as a function of temperature at a given ACSF composition. Elevation of [K +] o, [Mg 2+] o, or [H +] o all reduced the PS amplitude at low temperature, whereas elevation of [Ca 2+] o increased the PS amplitude. In conclusion, changes in the ionic microenvironment occurring during entrance into hibernation presumably result in depression of synaptic transmission at low temperatures in the hamsters hippocampus. The modulatory effect of ionic changes may be an important factor supporting a general depression of the brain during entrance into hibernation.
Published Version
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