Electrophysiological properties of neocortical neurons in vitro

Abstract

1. Intracellular recordings were obtained from neurons of the guinea pig sensorimotor cortical slice maintained in vitro. Under control recording conditions input resistances, time constants, and spiking characteristics of slice neurons were well within the ranges reported by other investigators for neocortical neurons in situ. However, resting potentials (mean of -75 mV) and spike amplitudes (mean of 93.5 mV) were 10-25 mV greater than has been observed in intact preparations. 2. Current-voltage relationships obtained under current clamp revealed a spectrum of membrane-rectifying properties at potentials that were subthreshold for spike generation. Ionic and pharmacologic analyses suggest that subthreshold membrane behavior is dominated by voltage-sensitive, very slowly inactivating conductances to K+ and Na+. 3. Action potentials were predominantly Na+ dependent under normal conditions but when outward K+ currents were reduced pharmacologically, it was possible, in most cells, to evoke a non-Na+-dependent, tetrodotoxin-(TTX) insensitive spike, which was followed by a prominent depolarizing after-potential. Both of these events were blocked by the Ca2+ current antagonists, Co2+ and Mn2+. 4. A small population of neurons generated intrinsic, all-or-none burst potentials when depolarized with current pulses or by synaptic activation. These cells were located at a narrow range of depths comprising layer IV and the more superficial parts of layer V. 5. Spontaneous excitatory synaptic potentials appeared in all neurons. Spontaneous inhibitory events were visible in only about 10% of the cells, and in those cases apparently reversed polarity at a level slightly positive to resting potential. Stimulation of the surface of the slice at low intensities evoked robust and usually concurrent excitatory and inhibitory synaptic potentials. Unitary inhibitory postsynaptic potentials (IPSPs) reversed at levels positive to rest. Stronger stimulation produced a labile, long-duration, hyperpolarizing IPSP with a reversal potential 15-20 mV negative to the resting level. 6. Neocortical neurons in vitro retain the basic membrane and synaptic properties ascribed to them in situ. However, the array of passive and active membrane behavior observed in the slice suggests that cortical neurons may be differentiated by specific functional properties as well as by their extensive morphological diversity.

Dopamine D1 and D4 Receptor Subtypes Differentially Modulate Recurrent Excitatory Synapses in Prefrontal Cortical Pyramidal Neurons

“…The late EPSPs reported here by afferent stimulation in slices taken from developmentally mature rats (ie 6-8 weeks; Zhu, 2000) resemble the late EPSPs evoked in layer II/III frontal cortical pyramidal neurons by intracortical stimulation in slices from young prepubertal rats (o6 weeks; 120-150 g; Sutor and Hablitz, 1989) or in guinea-pig neocortical neurons that were characterized as stimulus intensity sensitive (Connors et al, 1982), as similarly reported here (see Figure 8). These neurons, which were mostly recovered in cortical deep layer V following intracellular recording/ labeling, had axons which ramified extensively and ascended to superficial layers, in addition to giving off several secondary axons that target subcortical structures (see Figure 1c).…”

Pattern Formation in a Network of Excitatory and Inhibitory Cells with Adaptation

“…The network model consists of two homogeneous populations of neurons, one excitatory (E), displaying adaptation, and the other one inhibitory (I), without adaptation. This is a reasonable assumption, for example, for cortical neurons, since experimental studies report that in the cortex most of the inhibitory neurons do not display spike adaptation [3], [4], [14].…”

Inhibitory control of somatodendritic interactions underlying action potentials in neocortical pyramidal neurons in vivo: An intracellular and computational study

“…1A-C) that had resting potentials _ 60 mV and APs ranging between 55 and 80 mV (n=82). All but two of the morphologically-identified cells (n=42) were regular spiking 6,45 pyramidal neurons ( Figs 1D, 2A-B) whose somata were located in the infragranular (n=24) or supragranular layers (n=16), 1 to 2 mm from the cortical stimulating electrode array (Fig. 1A-B).…”