Caspase-3 activity in hippocampal slices reflects changes in synaptic plasticity

Electrophysiological measures of the functional activity of neurons in field CA1 in conditions of paired-pulse stimulation of Schäffer collaterals were performed in relation to the involvement of caspase-3 in mediating neuroplasticity; the relationship between functional activity and caspase-3 activity in hippocampal slices from Wistar rats was addressed. Enzyme activity was assessed in each individual slice at the end of the electrophysiological experiment. The results obtained here showed that the highest level of enzyme activity was seen when the efficiency of interneuronal interactions decreased. Nerve cell excitability showed no changes; interactions increasing synaptic efficiency, particularly in paired-pulse stimulation, produced normal response amplitudes. Further deterioration of the functional state of slices and impairments in spike generation were accompanied by increases in caspase-3 activity to the normal level. Increases in the activity of another proteinase, cathepsin B, were generally seen in any deviation from normal functioning, though there was no correlation with any of the electrophysiological parameters. It is suggested that high caspase-3 activity in slices is linked with neuroplastic processes in synapses and has no direct relationship to nerve cell apoptosis.