Fig. 4.
Propagation and spread of regenerative potentials along the apical dendrite. A, Schematic drawing of recording pipettes indicates the locations of the dendritic (809, 657, and 338 μm distal from the soma) and somatic recordings in two triple recordings from the same cell. The length of the apical dendrite was 1232 μm. B, Responses in the dendritic tufts (809 μm), distal dendritic trunk (657 μm), and soma to step-depolarizing current injections at the tufts of the same neuron. Note that the regenerative potential began first in the primary tufts, propagated to the distal dendritic trunk with little attenuation in amplitude, and was followed by the somatic action potentials. C, Threshold for dendritic regenerative potentials evoked by current injection in the primary tufts or distal trunks. D, Amplitude of dendritic regenerative potentials in the primary tufts and distal trunks in response to current injection in the primary tufts.E, Responses of the dendritic tufts (809 μm), proximal dendritic trunk (338 μm), and soma to step-depolarizing current injections at the tufts of the same neuron. Note that the regenerative potential started first in the primary tufts, propagated to the proximal dendritic trunk with intermediate attenuation in amplitude, and was followed by the somatic action potentials. The full-amplitude regenerative potentials in the proximal trunk were generated after the somatic action potentials. The resting membrane potential at the soma was −79 mV. The resting membrane potentials at the dendrite from distal to proximal were −68, −68, and −77 mV, respectively.F, Responses in a secondary dendritic tuft branch (P2; 869 μm), a primary dendritic tuft branch (P3; 706 μm), the proximal dendritic trunk (P4; 225 μm), and soma (P1) to step-depolarizing current injections at the distal tuft branch of another neuron. Note that the regenerative potential began first in the secondary tuft, propagated to the primary tuft with little attenuation in amplitude, and was followed by the full-amplitude regenerative action potentials first in the proximal dendrite and then in the soma. The resting membrane potential at the soma was −80 mV. The resting membrane potentials at the dendrite from distal to proximal were −68, −69, and −75 mV, respectively. The calibration applies to B, E, F.