Abstract
Axon and dendrite play different roles in neuronal signal transduction. A neuron receives signals in dendrites and sends signal out via axon. Differences between axon and dendrite are resulted from various regulation processes during development. Higher tubulin acetylation and tyrosination are observed in axonal microtubules. One of the major axonal microtubule-associated protein (MAP) is tau, while one major dendritic MAP is MAP2. To study the spatial and temporal variations of microtubules and MAPs in axon, immunofluorescence staining was used. By studying the fluorescence distribution of MAP2, dephosphorylated tau, acetylated tubulin and tyrosinated tubulin, I found that the contents of these antigens in the distal halves were higher than in the proximal halves of axons on 8th day in vitro (DIV8). On the other hand, dephosphorylated tau and tyrosinated tubulin were preferentially localized to distal halves of axons since DIV4. MAP2 and acetylated tubulin distributed rather evenly along axons on DIV4 and gradually distributed preferentially to distal axon until DIV8. Furthermore, fluorescence density (fluorescence/pixel) in axon and dendrite were also calculated. Tyrosinated tubulin immunoreactivity exhibited similar fluorescence density in axons and dendrites; dephosphorylated tau and acetylated tubulin immunoreactivities exhibited higher density in axons than in dendrites; the immunoreactivity density of MAP2 changed between DIV4 to DIV8. Conclusively, my study illustrated the changes of the distribution of microtubules and MAPs in axons during the in vitro development of cultured rat hippocampal neurons. The possible functions of these changes in the development of axons in neurons are also discussed.