Changes in the activity of complex spikes of the dentate gyrus and CA1 region of hippocampus induced by noxious stimulation

摘要

Extracellular recordings in the CA1 region of the hippocampus and dentate gyrus, in urethane anaesthetized rats, identified four types of neuronal activity, which according to their firing pattern corresponded to the so-called complex spikes. This report shows that a brief noxious stimulus, applied to the tail of the animal, induced an increase in the duration of the inter-spike intervals of some complex spikes. Inter-spike intervals of cells that discharged bursts of two action potentials in the dentate gyrus was increased at the beginning of the noxious stimulus, while the end of the stimulus seems to be signaled by an increase in the duration of the second inter-spike interval of neurons that discharge three action potentials. Moreover, in the CA1 region of the hippocampus, complex spike cells discharging bursts of four spikes, increased the duration of the third inter-spikes interval at the end of the noxious stimulus, suggesting that these cells too, would be involved in temporal coding of the noxious stimulus. These findings suggest that at least, in urethane anesthetized rats, some neurons in the hippocampal formation discharging complex spikes appear to signal the onset and duration of nociceptive information by changes in the duration of some inter-spike intervals.