The permeation and activation properties of brain sodium channels change during development.
BTX-modified sodium channels from 15-day embryonic (E15) rat forebrains were studied in planar lipid bilayers. Compared to postnatal sodium channels, E15 channels had a lower maximal single channel conductance, whereas their permeation pathway sensed a comparable surface charge density and had a similar apparent binding affinity for sodium ions. The steady-state activation curve of E15 channels was significantly more hyperpolarized and had a shallower slope than postnatal channels. The apparent BTX binding affinity was significantly lower for E15 channels than for postnatal channels. Finally, E15 channel alpha-subunits displayed a lower apparent molecular weight, and a lower sialylation level than postnatal sodium channel alpha-subunits. Together with previous studies, our data suggested that the observed functional differences between E15 and postnatal voltage-dependent sodium channels cannot be explained solely by the observed differences in channel sialylation, and hence they also appeared to reflect the presence of other channel structural differences.
Castillo
Cecilia
C
Instituto de Estudios Avanzados, Apartado 17606, 1015-A, Caracas, Venezuela. ccastill@racciun.ve
Thornhill
William B
WB
Zhu
Jing
J
Recio-Pinto
Esperanza
E
D000818:Animals; D001496:Batrachotoxins / Q000494:pharmacology*; D001921:Brain / Q000033:anatomy & histology / Q000187:drug effects / Q000196:embryology* / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D004553:Electric Conductivity; D005314:Embryonic and Fetal Development / Q000502:physiology*; D015151:Immunoblotting / Q000379:methods; D008051:Lipid Bilayers / Q000378:metabolism; D008564:Membrane Potentials; D009439:Neuraminidase / Q000494:pharmacology; D018408:Patch-Clamp Techniques / Q000295:instrumentation / Q000379:methods; D010539:Permeability; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000276:immunology / Q000502:physiology*
D001496:Batrachotoxins; D008051:Lipid Bilayers; D021122:Protein Subunits; D015222:Sodium Channels; D012964:Sodium; D009439:Neuraminidase