Neuronal excitability and sensory responsiveness in the thalamo‐cortical network in a novel rat model of isoelectric brain state

Abstract

The neuronal and network properties that persist during an isoelectric coma remain largely unknown. r We developed a new in vivo rat model to assess cell excitability and sensory responsiveness in the thalamo-cortical pathway during an isoflurane-induced isoelectric brain state. r The isoelectric electrocorticogram reflected a complete interruption of spontaneous synaptic and firing activities in cortical and thalamic neurons. r Cell excitability and sensory responses in the thalamo-cortical network persisted at a reduced level in the isoelectric condition and returned to control values after resumption of background brain activity. r These findings could lead to a reassessment of the functional status of the drug-induced isoelectric state: a latent state in which individual neurons and networks retain to some extent the ability of being activated by external inputs.

In vivo low‐intensity magnetic pulses durably alter neocortical neuron excitability and spontaneous activity

“…Indeed, the initial reduction in R m and τ m , which attenuates neuronal responsiveness to their synaptic inputs, would explain both the reduced amplitude of V m fluctuations and membrane hyperpolarization. Given the inverse correlation linking current firing threshold to V m in cortical neurons (Altwegg‐Boussac et al., 2014; Carton‐Leclercq et al., 2021), the membrane hyperpolarization would in turn explain the rightward shift of input–output relations and the reduced intrinsic excitability. Finally, all these cellular modifications will combine to reduce the efficiency with which cortical neurons process synaptic currents and generate APs and, thus, explain the progressive decrease of spontaneous firing.…”

In vivolow-intensity magnetic pulses durably alter neocortical neuron excitability and spontaneous activity

“…Indeed, the initial reduction in Rm and τm, which attenuates neuronal responsiveness to their synaptic inputs, would explain both the reduced amplitude of Vm fluctuations and membrane hyperpolarization. Given the inverse correlation linking current firing threshold to Vm in cortical neurons (Altwegg-Boussac et al, 2014; Carton-Leclercq et al, 2021), the membrane hyperpolarization would in turn explain the rightward shift of input-output relations and the reduced intrinsic excitability. Finally, all these cellular modifications will combine to reduce the efficiency with which cortical neurons process synaptic currents and generate APs and, thus, explain the progressive decrease of spontaneous firing.…”

Variation and convergence in the morpho-functional properties of the mammalian neocortex

“…Comparative analysis of the electrical properties of pyramidal neurons between species, and even within the same species, based on in vitro studies carried out by different laboratories can prove difficult due to the many experimental factors (e.g., the animal age, composition of intracellular and extracellular solutions, recording temperature or degree of damage to the dendritic tree during slices preparation) that vary from one study to another and are known to affect the synaptic and biophysical properties of neuronal membranes (Hardingham and Larkman, 1998 ; Zhu, 2000 ; Bekkers and Häusser, 2007 ). The task becomes even more complex when considering in vivo studies, as the background synaptic activity that characterises intact brain preparations is known to have a significant impact on the excitability and firing of cortical neurons (Destexhe et al, 2003 ; Altwegg-Boussac et al, 2014 ; Carton-Leclercq et al, 2021 ). The increase in the number of data sets and the integration of work combining experiments carried out on several species in a single study have nevertheless enabled a number of electrophysiological characteristics to be compared reliably.…”