Axonal action-potential initiation and Na+ channel densities in the soma and axon initial segment of subicular pyramidal neurons. Export

@article{citeulike:5294748, abstract = {A long-standing hypothesis is that action potentials initiate first in the axon hillock/initial segment (AH-IS) region because of a locally high density of Na+ channels. We tested this idea in subicular pyramidal neurons by using patch-clamp recordings in hippocampal slices. Simultaneous recordings from the soma and IS confirmed that orthodromic action potentials initiated in the axon and then invaded the soma. However, blocking Na+ channels in the AH-IS with locally applied tetrodotoxin (TTX) did not raise the somatic threshold membrane potential for orthodromic spikes. TTX applied to the axon beyond the AH-IS (30-60 microm from the soma) raised the apparent somatic threshold by approximately 8 mV. We estimated the Na+ current density in the AH-IS and somatic membranes by using cell-attached patch-clamp recordings and found similar magnitudes (3-4 pA/microm2). Thus, the present results suggest that orthodromic action potentials initiate in the axon beyond the AH-IS and that the minimum threshold for spike initiation of the neuron is not determined by a high density of Na+ channels in the AH-IS region.}, author = {Colbert, C. M. and Johnston, D.}, citeulike-article-id = {5294748}, citeulike-linkout-0 = {http://view.ncbi.nlm.nih.gov/pubmed/8824308}, citeulike-linkout-1 = {http://www.hubmed.org/display.cgi?uids=8824308}, day = {1}, issn = {0270-6474}, journal = {The Journal of neuroscience : the official journal of the Society for Neuroscience}, keywords = {axon, cortex, spike\_initiation}, month = {November}, number = {21}, pages = {6676--6686}, posted-at = {2009-07-28 20:29:52}, priority = {2}, title = {Axonal action-potential initiation and Na+ channel densities in the soma and axon initial segment of subicular pyramidal neurons.}, url = {http://view.ncbi.nlm.nih.gov/pubmed/8824308}, volume = {16}, year = {1996} }

TY - JOUR ID - citeulike:5294748 L3 - citeulike-article-id:5294748 N2 - A long-standing hypothesis is that action potentials initiate first in the axon hillock/initial segment (AH-IS) region because of a locally high density of Na+ channels. We tested this idea in subicular pyramidal neurons by using patch-clamp recordings in hippocampal slices. Simultaneous recordings from the soma and IS confirmed that orthodromic action potentials initiated in the axon and then invaded the soma. However, blocking Na+ channels in the AH-IS with locally applied tetrodotoxin (TTX) did not raise the somatic threshold membrane potential for orthodromic spikes. TTX applied to the axon beyond the AH-IS (30-60 microm from the soma) raised the apparent somatic threshold by approximately 8 mV. We estimated the Na+ current density in the AH-IS and somatic membranes by using cell-attached patch-clamp recordings and found similar magnitudes (3-4 pA/microm2). Thus, the present results suggest that orthodromic action potentials initiate in the axon beyond the AH-IS and that the minimum threshold for spike initiation of the neuron is not determined by a high density of Na+ channels in the AH-IS region. IS - 21 JF - The Journal of neuroscience : the official journal of the Society for Neuroscience SN - 0270-6474 EP - 6686 TI - Axonal action-potential initiation and Na+ channel densities in the soma and axon initial segment of subicular pyramidal neurons. VL - 16 SP - 6676 KW - axon KW - cortex KW - spike_initiation AU - Colbert, CM AU - Johnston, D PY - 1996/11/01/ UR - http://view.ncbi.nlm.nih.gov/pubmed/8824308 ER -