[Expression changes of Na channel subunits correlate with developmental maturation of electrophysiological characteristics of rat cerebellar Purkinje neurons].

OBJECTIVE

To investigate the variations in the expression of voltage-gated sodium (Na) channel subunits during development of rat cerebellar Purkinje neurons and their correlation with maturation of electrophysiological characteristics of the neurons.

METHODS

We observed the changes in the expression levels of Na1.1, 1.2, 1.3 and 1.6 during the development of Purkinje neurons using immunohistochemistry in neonatal (5-7 days after birth), juvenile (12-14 days), adolescent (21-24 days), and adult (42-60 days) SD rats. Using whole-cell patch-clamp technique, we recorded the spontaneous electrical activity of the neurons in ex vivo brain slices of rats of different ages to analyze the changes of electrophysiological characteristics of these neurons during development.

RESULTS

The expression of Na subunits in rat cerebellar Purkinje neurons showed significant variations during development. Na1.1 subunit was highly expressed throughout the developmental stages and increased progressively with age ( < 0.05). Na1.2 expression was not detected in the neurons in any of the developmental stages ( > 0.05). The expression level of Na1.3 decreased with development and became undetectable after adolescence ( < 0.05). Na1.6 expression was not detected during infancy, but increased with further development ( < 0.05). Na1.1 and Na1.3 were mainly expressed in the early stages of development. With the maturation of the rats, Na1.3 expression disappeared and Na1.6 expression increased in the neurons. Na1.1 and Na1.6 were mainly expressed after adolescence. The total Na protein level increased gradually with development ( < 0.05) and tended to stabilize after adolescence. The spontaneous frequency and excitability of the Purkinje neurons increased gradually with development and reached the mature levels in adolescence. The developmental expression of Na subunits was positively correlated with discharge frequency (=0.9942, < 0.05) and negatively correlated with the excitatory threshold of the neurons (=0.9891, < 0.05).

CONCLUSION

The changes in the expression levels of Na subunits are correlated with the maturation of high frequency electrophysiological properties of the neurons, suggesting thatmature Na subunit expressions is the basis of maturation of electrophysiological characteristics of the neurons.