DEVELOPMENTAL-CHANGES OF PROTEINS ASSOCIATED WITH N-TYPE CALCIUM CHANNELS IN THE RAT-BRAIN

We have previously reported that two monoclonal antibodies (SpM-1 and SPM-2) recognizing 36-kDa and 28-kDa proteins, respectively, immunoprecipitated significant fractions of omega-conotoxin-sensitive calcium channels solubilized from the brain. Localization of the immunoreactivities for these antibodies was examined immunohistochemically in adult and developing rat brains. The distribution of both immunoreactivities was identical and widely observed in synaptic regions throughout the brain, although the various portions of the brain showed their own characteristic antigen distribution. There were marked differences in staining intensity among the various brain regions: the most intense immunoreactivity was found in the cortex in all parts of the brain, various nuclei, the median eminence, limbic system and related areas including the hippocampus, septum, amygdala, and olfactory bulb. Immunoreactivity for both proteins tended to increase during the development, showing a strong correlation with synaptic development. In the cerebellar cortex, staining with these antibodies showed the migration of Purkinje cells. Until 7 days after birth, many Purkinje cells, surrounded by immunopositive synapses, were found in the granule cell layer, and then the cells moved to the border between the molecular and granule cell layers. In the hippocampus, the immunoreactivity was weak before birth, but increased markedly within 17 days after birth. Immunoblot analysis also confirmed the heterogeneous distribution and molecular diversity of the immunoreactive antigens in different stages of the brain.