Activity-dependent slow hyperpolarization in cat sensorimotor cortex in vitro.
The synaptic regulatory mechanism of resting membrane potential of layer III and V pyramidal neurons was analyzed intracellularly in the slice preparation of cat sensorimotor cortex. During the tetanic stimulation of white matter, subthreshold membrane depolarization was induced, and after that, a slowly developing hyperpolarization was induced in the normal solution. When the membrane potential showed a slow change, spike duration and input resistance did not change and evoked single synaptic response did not reveal the enhancement of slow IPSPs. However, afterhyperpolarization following action potential was enhanced. The slow hyperpolarization and the enhancement of afterhyperpolarization were not observed in the cells treated with an NMDA receptor antagonist or a calcium channel blocker Ni(2+) (50-100 microM), or the cells hyperpolarized more than -80 mV before the tetanic stimulation.