TY - JOUR
T1 - Properties of K+ Conductances in Cat Retinal Ganglion Cells During the Period of Activity‐mediated Refinements in Retinofugal Pathways
AU - Skaliora, I.
AU - Robinson, D. W.
AU - Scobey, R. P.
AU - Chalupa, L. M.
N1 - Copyright:
Copyright 2016 Elsevier B.V., All rights reserved.
PY - 1995/7
Y1 - 1995/7
N2 - During ontogeny retinal ganglion cells manifest pronounced changes in excitable membrane properties. To further our understanding of the ionic conductances underlying such functional changes, the whole‐cell voltage‐clamp variation of the patch‐clamp technique was used to record potassium currents in 220 ganglion cells dissociated from cat retinas ranging in age from embryonic day 31 to postnatal day 10. Potassium currents were isolated by blocking voltage‐gated Na+ and Ca2+ currents with tetrodoxin (TTX) and CoCl2 respectively and were characterized by their pharmacology, kinetics and voltage‐dependence of activation and inactivation. In all cases, a combination of three currents accounted for the total outward calcium‐independent K+ current: (i) a steady linear conductance; (ii) a voltage‐gated transient current, lA, and (iii) a voltage‐gated sustained current, lk. Both voltage‐gated currents were affected by the application of 4‐aminopyridine and tetraethylammonia (TEA): lA showed a greater sensitivity to 4‐aminopyridine, while lk was more sensitive to TEA. Both voltagegated currents were present throughout the developmental period examined; however, the percentage of retinal ganglion cells (RGCs) expressing lA showed a marked decline from 82% at E31 to 45% at postnatal ages. During this developmental period there was an increase in the density of the two voltage‐gated and the linear conductance. Additionally, with maturation, significantly slower inactivation kinetics were observed for lK. These findings, and our previous results dealing with maturational changes in the TTX‐sensitive voltage‐gated Na current, are related to the generation of excitability in developing retinal ganglion cells. Furthermore, the presence of cells with and without transient K+ conductance throughout development suggests that the different spiking patterns observed in RGC classes may be partially due to differences in their membrane properties.
AB - During ontogeny retinal ganglion cells manifest pronounced changes in excitable membrane properties. To further our understanding of the ionic conductances underlying such functional changes, the whole‐cell voltage‐clamp variation of the patch‐clamp technique was used to record potassium currents in 220 ganglion cells dissociated from cat retinas ranging in age from embryonic day 31 to postnatal day 10. Potassium currents were isolated by blocking voltage‐gated Na+ and Ca2+ currents with tetrodoxin (TTX) and CoCl2 respectively and were characterized by their pharmacology, kinetics and voltage‐dependence of activation and inactivation. In all cases, a combination of three currents accounted for the total outward calcium‐independent K+ current: (i) a steady linear conductance; (ii) a voltage‐gated transient current, lA, and (iii) a voltage‐gated sustained current, lk. Both voltage‐gated currents were affected by the application of 4‐aminopyridine and tetraethylammonia (TEA): lA showed a greater sensitivity to 4‐aminopyridine, while lk was more sensitive to TEA. Both voltagegated currents were present throughout the developmental period examined; however, the percentage of retinal ganglion cells (RGCs) expressing lA showed a marked decline from 82% at E31 to 45% at postnatal ages. During this developmental period there was an increase in the density of the two voltage‐gated and the linear conductance. Additionally, with maturation, significantly slower inactivation kinetics were observed for lK. These findings, and our previous results dealing with maturational changes in the TTX‐sensitive voltage‐gated Na current, are related to the generation of excitability in developing retinal ganglion cells. Furthermore, the presence of cells with and without transient K+ conductance throughout development suggests that the different spiking patterns observed in RGC classes may be partially due to differences in their membrane properties.
KW - development
KW - ion channels
KW - linear conductance
KW - patch‐clamp recordings
KW - potassium currents
UR - http://www.scopus.com/inward/record.url?scp=0029034577&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0029034577&partnerID=8YFLogxK
U2 - 10.1111/j.1460-9568.1995.tb01151.x
DO - 10.1111/j.1460-9568.1995.tb01151.x
M3 - Article
C2 - 7551182
AN - SCOPUS:0029034577
SN - 0953-816X
VL - 7
SP - 1558
EP - 1568
JO - European Journal of Neuroscience
JF - European Journal of Neuroscience
IS - 7
ER -