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Published on: March 23, 2011
[Changes of Na(+) channels in rat hippocampal CA1 neurons in early development after birth]
Jia-Qi Qiao1, Ai-Li Liu, Tiao-Tiao Liu
1School of Biomedical Engineering, Research Center of Basic Medical Science, Tianjin Medical University, Tianjin 300070, China.
Insights
The critical period for voltage-gated sodium channel (Na(+) channel) development in rat hippocampal CA1 neurons is between 1-2 weeks after birth. This period shows significant increases in Na(+) channel density, altered activation, and faster inactivation.
Area of Science:
- Neuroscience
- Developmental Biology
- Electrophysiology
Background:
- Voltage-gated sodium channels (Na(+) channels) are crucial for neuronal excitability.
- Understanding the developmental timeline of these channels in the hippocampus is essential for comprehending neural circuit maturation.
Purpose of the Study:
- To investigate the critical developmental period of voltage-gated Na(+) channels in hippocampal CA1 neurons of rats.
- To characterize age-dependent changes in Na(+) channel properties during early postnatal development.
Main Methods:
- Whole-cell patch-clamp recordings were performed on acutely isolated hippocampal CA1 neurons from rats aged 0-4 weeks.
- Sodium (Na(+)) currents were analyzed to assess changes in current density, activation, inactivation, and recovery from inactivation.
Main Results:
- Na(+) channel current density significantly increased with age, with the most substantial rise observed between 1-2 weeks post-birth.
- The activation curve of Na(+) channels shifted leftward, indicating altered voltage dependence, and inactivation rates increased during this critical period.
- Changes in action potential properties correlated with the observed alterations in Na(+) channel function.
Conclusions:
- The period of 1-2 weeks after birth represents a critical developmental window for voltage-gated Na(+) channels in hippocampal CA1 neurons.
- During this period, significant increases in Na(+) channel distribution, leftward shifts in activation, accelerated inactivation, and shortened recovery times occur, influencing neuronal excitability.
Abstract:
The purpose of this research is to investigate the critical period of voltage-gated Na(+) channel development in hippocampal CA1 neurons. Changes of Na(+) currents in acutely isolated hippocampal CA1 neurons of rats at different ages (0-4 weeks after birth) were recorded using the whole-cell patch-clamp technique. The results indicated that the maximum current density of Na(+) channels was increasing with age, and the amplitudes in 1, 2, 3 and 4 weeks respectively grew by (42.76 ± 4.91)%, (146.80 ± 7.63)%, (208.79 ± 5.28)% and (253.72 ± 5.74)% (n = 10, P < 0.05) compared with that in 0 week. The current density in CA1 neurons of 1-2 weeks after birth increased more significantly than those of other groups. The activation curve of Na(+) channel shifted to the left. The half-activation voltages (mV) in 0-2 weeks were -39.06 ± 0.65, -43.41 ± 0.52, -48.29 ± 0.45 (n = 10, P < 0.05), respectively, showing significant age-dependent decrease, and there were no significant changes in other groups. The slope factors of activation curve for each group did not change significantly. There were no regular changes in inactivation curve and no significant changes in half-inactivation voltage. The slope factors of inactivation curve in 1-2 weeks were: 5.77 ± 0.56, 4.42 ± 0.43 (n = 10, P < 0.05). The inactivation rate of the second week after birth was faster than that of the first week, and there were no significant changes during 0-1 week and 2-4 weeks. The recovery from inactivation curve of Na(+) channel shifted to the left. The recovery time declined in 1-3 weeks. Changes of action potential properties were consistent with Na(+) current. These results suggest that the period of 1-2 weeks after birth may be the critical development period of voltage-gated Na(+) channel in hippocampal CA1 neurons. During this time, the distribution of Na(+) channel increases significantly; the activation curve of Na(+) channel shifts to the left; inactivation rate increases as well as recovery time shortens.
