The permeation and activation properties of brain sodium channels change during development |
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Authors: | Castillo Cecilia Thornhill William B Zhu Jing Recio-Pinto Esperanza |
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Institution: | Instituto de Estudios Avanzados, Apartado 17606, 1015-A, Caracas, Venezuela. ccastill@racciun.ve |
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Abstract: | 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. |
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