PT  - JOURNAL ARTICLE
AU  - Alessandro R. Galloni
AU  - Aeron Laffere
AU  - Ede A. Rancz
TI  - Apical length modulates dendritic excitability in L5 pyramidal neurons
AID  - 10.1101/754499
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 754499
4099  - http://biorxiv.org/content/early/2019/09/04/754499.short
4100  - http://biorxiv.org/content/early/2019/09/04/754499.full
AB  - Thick-tufted layer 5 (ttL5) pyramidal neurons are known for their complex morphology and diverse set of active conductances which support highly nonlinear dendritic computations. This knowledge is based primarily on recordings from neurons in the rat primary visual (V1) and somatosensory cortices. Here, we compare the active properties of mouse ttL5 neurons in V1 and in the medial secondary visual cortex (V2m) using patch-clamp recordings in acute brain slices. We find that V2m neurons lack the characteristic hallmarks of dendritic Ca2+ plateaus that are found in V1 neurons. Neurons in V2m also have shorter apical dendrites and we find a correlation between trunk length and excitability. Compartmental biophysical modelling revealed that the length of the apical trunk is indeed a crucial factor for determining the effect of backpropagating action potentials (bAPs) on the apical compartments. In both morphologically detailed and reduced models, neurons with short apical trunk did not display BAC firing. Finally, in the reduced model we show that peak tuft voltage increased as a function of trunk length due to a Na+ channel-dependent sustained broadening of bAPs in the distal trunk of long neurons. In summary, we show that ttL5 neuron active properties are not universal throughout the brain and provide new insights into how dendritic excitability can be modulated by apical dendrite length.