TY - JOUR
T1 - Sodium-dependent regenerative responses in dendrites of axotomized motoneurons in the cat
AU - Sernagor, E.
AU - Yarom, Y.
AU - Werman, R.
PY - 1986
Y1 - 1986
N2 - Ten days after extradural axotomy, partial spikes are found in >20% of cat L7 motoneurons, while 15-21 days after axotomy the incidence increases to 60%. These responses are produced in excitable (hot) spots in the dendrites by synaptic excitation. Intracellular injection of QX-314, a lidocaine derivative and effective blocker of Na+ channels from within neurons, results in elimination of partial spikes before blocking somadendritic spikes. The action of QX-314 does not depend on changes in passive membrane properties or on changes in synaptic properties. Injection of Cs+ and Cl- ions rule out any major role for calcium, potassium, or chloride currents in the production of partial spikes. The partial spikes represent an unusual Na+-dependent dendritic phenomenon induced by axotomy when carried out relatively near the soma. It is reasonable to postulate that the partial spikes result from a higher concentration of Na+ channels in the dendrites. This may be the consequence of a high rate of production of Na+-channel proteins that are intended for the cut end of the axon; alternatively, they may result from the reflection from the cut end of such proteins produced at either a normal or an increased rate. These aberrant channels are inserted into somatic and dendritic membranes in higher concentrations than normal and, as well as producing local dendritic regions of low safety factor responsible for the partial spikes, also produce somadendritic spikes of unusually fast rise time and lower than unsual threshold, which are relatively resistant to QX-314.
AB - Ten days after extradural axotomy, partial spikes are found in >20% of cat L7 motoneurons, while 15-21 days after axotomy the incidence increases to 60%. These responses are produced in excitable (hot) spots in the dendrites by synaptic excitation. Intracellular injection of QX-314, a lidocaine derivative and effective blocker of Na+ channels from within neurons, results in elimination of partial spikes before blocking somadendritic spikes. The action of QX-314 does not depend on changes in passive membrane properties or on changes in synaptic properties. Injection of Cs+ and Cl- ions rule out any major role for calcium, potassium, or chloride currents in the production of partial spikes. The partial spikes represent an unusual Na+-dependent dendritic phenomenon induced by axotomy when carried out relatively near the soma. It is reasonable to postulate that the partial spikes result from a higher concentration of Na+ channels in the dendrites. This may be the consequence of a high rate of production of Na+-channel proteins that are intended for the cut end of the axon; alternatively, they may result from the reflection from the cut end of such proteins produced at either a normal or an increased rate. These aberrant channels are inserted into somatic and dendritic membranes in higher concentrations than normal and, as well as producing local dendritic regions of low safety factor responsible for the partial spikes, also produce somadendritic spikes of unusually fast rise time and lower than unsual threshold, which are relatively resistant to QX-314.
UR - http://www.scopus.com/inward/record.url?scp=0012088141&partnerID=8YFLogxK
U2 - 10.1073/pnas.83.20.7966
DO - 10.1073/pnas.83.20.7966
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C2 - 2429323
AN - SCOPUS:0012088141
SN - 0027-8424
VL - 83
SP - 7966
EP - 7970
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 20
ER -