Premium
Direct demonstration of persistent Na + channel activity in dendritic processes of mammalian cortical neurones
Author(s) -
Magistretti Jacopo,
Ragsdale David S.,
Alonso Angel
Publication year - 1999
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1999.00629.x
Subject(s) - conductance , chemistry , electrophysiology , biophysics , ion channel , entorhinal cortex , patch clamp , sodium channel , soma , anatomy , neuroscience , physics , sodium , biology , hippocampus , receptor , biochemistry , organic chemistry , condensed matter physics
1 Single Na + channel activity was recorded in patch‐clamp, cell‐attached experiments performed on dendritic processes of acutely isolated principal neurones from rat entorhinal‐cortex layer II. The distances of the recording sites from the soma ranged from ≈20 to ≈100 μm. 2 Step depolarisations from holding potentials of −120 to −100 mV to test potentials of −60 to +10 mV elicited Na + channel openings in all of the recorded patches ( n = 16 ). 3 In 10 patches, besides transient Na + channel openings clustered within the first few milliseconds of the depolarising pulses, prolonged and/or late Na + channel openings were also regularly observed. This ‘persistent’ Na + channel activity produced net inward, persistent currents in ensemble‐average traces, and remained stable over the entire duration of the experiments (≈9 to 30 min). 4 Two of these patches contained <= 3 channels. In these cases, persistent Na + channel openings could be attributed to the activity of one single channel. 5 The voltage dependence of persistent‐current amplitude in ensemble‐average traces closely resembled that of whole‐cell, persistent Na + current expressed by the same neurones, and displayed the same characteristic low threshold of activation. 6 Dendritic, persistent Na + channel openings had relatively high single‐channel conductance (≈20 pS), similar to what is observed for somatic, persistent Na + channels. 7 We conclude that a stable, persistent Na + channel activity is expressed by proximal dendrites of entorhinal‐cortex layer II principal neurones, and can contribute a significant low‐threshold, persistent Na + current to the dendritic processing of excitatory synaptic inputs.