Fig. 3.

Field, extracellular K⁺ concentration ([K⁺]_o), and intracellular recordings obtained in vitro during LVF-onset seizure-like dischargers. A: simultaneous field (Field) and intracellular (−68 mV) recordings obtained from the entorhinal cortex of a rat brain slice during bath application of 4-aminopyridine; in this and the following panels the dotted lines indicate the resting membrane potential of the neuron recorded intracellularly. Traces shown in the inset were obtained from a different neuron during active depolarization with intracellular current from a resting membrane potential at approximately −62 mV. B: field and [K⁺]_o activities recorded during application of 4-aminopyridine from the deep layers of the rat entorhinal cortex; the dotted line indicates the [K⁺]_o base level. C: simultaneous field and intracellular (−65 mV) recordings obtained from a principal cell in the entorhinal cortex during the perfusion of 50 μM bicuculline for 3 min in the in vitro isolated guinea pig brain. The spectrogram on the top illustrates the fast activity at around 20 Hz at the onset of the seizure-like event. The fast activity occurring at the onset of the seizure-like discharge is expanded in the inset where the principal cell was depolarized by intracellular injection of steady current. D: field and intracellular recordings of the response induced by lateral olfactory tract stimulation in an entorhinal cortex neuron with a resting membrane potential of −60 mV. Note that the brief inhibitory postsynaptic potentials (IPSPs) that correlate to the fast activity oscillations have reversal potentials similar to what is seen with the lateral olfactory tract-evoked IPSP. E: simultaneous field and intracellular recordings from a principal cell in the perirhinal cortex of a rat brain slice during bath application of 4-aminopyridine; note that ictal discharge onset is characterized by preictal spiking acceleration as well as that both interictal (arrow) and “preictal” discharges consist of depolarizations with action potential bursts followed by a hyperpolarizing potential that progressively decreases in amplitude (arrowheads) and coincides with more intense action potential bursting. F: simultaneous field and [K⁺]_o recordings obtained in the deep layers of the perirhinal cortex during 4-aminopyridine application. Note the progressive increases in [K⁺]_o that accompany the preictal spikes up to ictal discharge initiation that coincide with values larger than 6.3 mM. Data were obtained during experiments that have been published by Avoli et al. (1996, 2013), Biagini et al. (2013), Gnatkovsky et al. (2008), Köhling et al. (2016), Lopantsev and Avoli (1998a and b), Trombin et al. (2011), and Uva et al. (2015).