Alexandre Guet McCreight,
Frances SkinnerGoogle Meet Link:
https://meet.google.com/ofz-cbmq-nwhThough the electrophysiology techniques that we use to probe neuronal function have made large advancements, neuronal function remains shrouded in mystery. Little is known about the current contributions that govern cell excitability across different neuronal subtypes and their dendritic compartments
in vivo. The picture that we do have is largely based on somatic recordings performed
in vitro.
Uncovering dendritic current contributions in neuron subtypes that represent a minority of the neuronal population is not currently a feasible task using purely experimental means. Thus, we employ morphologically-detailed multi-compartment models, and specifically, we use two models of a specific type of inhibitory interneuron, the oriens lacunosum moleculare (OLM) cell. The OLM cell is a well-studied cell type in CA1 hippocampus that is important in gating sensory and contextual information.
We use these models to assess the current contribution profile across the different somatic and dendritic compartments of the models in the presence of levels of synaptic bombardment that would occur
in vivo and compare them to corresponding
in vitro scenarios with somatic current injections that generate the same spike rates. Using this approach, we identify changes in dendritic excitability, current contributions, and current co-activation patterns.
We find that during
in vivo-like scenarios the relative timing between different channel current activation patterns and voltage are preserved. On the other hand, when compared across morphological compartments, current and voltage signals were more decorrelated during
in vivo-like scenarios, suggesting decreased signal propagation. We also observe that changes do occur during
in vivo-like scenarios on the level of relative current contribution profiles. More specifically, in addition to shifts in the relative balances of currents that are most active during spikes, we report robust enhancements in dendritic hyperpolarization-activated cyclic nucleotide-gated channel (HCN, or h-current) activation during
in vivo-like contexts. This suggests that dendritically-located h-channels are functionally important in altering signal propagation in the behaving animal.
[1] Guet-McCreight A and Skinner FK. [version 2; peer review: 2 approved]. F1000Research 2020, 9:180 (https://doi.org/10.12688/f1000research.22584.2)
