Abstract: Objective To investigate the variations in the expression of voltage-gated sodium (Nav) 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 NaV1.1, 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 NaV subunits in rat cerebellar Purkinje neurons showed significant variations during development. NaV1.1 subunit was highly expressed throughout the developmental stages and increased progressively with age (P<0.05). NaV1.2 expression was not detected in the neurons in any of the developmental stages (P>0.05). The expression level of NaV1.3 decreased with development and became undetectable after adolescence (P<0.05). NaV1.6 expression was not detected during infancy, but increased with further development (P<0.05). NaV1.1 and NaV1.3 were mainly expressed in the early stages of development. With the maturation of the rats, NaV1.3 expression disappeared and NaV1.6 expression increased in the neurons. NaV1.1 and NaV1.6 were mainly expressed after adolescence. The total NaV protein level increased gradually with development (P<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 NaV subunits was positively correlated with discharge frequency (r=0.9942, P<0.05) and negatively correlated with the excitatory threshold of the neurons (r=0.9891, P<0.05). Conclusion The changes in the expression levels of NaV subunits are correlated with the maturation of high frequency electrophysiological properties of the neurons, suggesting thatmature NaV subunit expressions is the basis of maturation of electrophysiological characteristics of the neurons.

Key words: voltage gated sodium channel; Purkinje neuron development; immunohistochemistry; spontaneous electrical activity; correlation analysis