CHANGES IN THE EXPRESSION OF SYNAPSIN-I AND SYNAPSIN-II MESSENGER-RNADURING POSTNATAL RAT-BRAIN DEVELOPMENT

Synapsin Ia, Ib, IIa, and IIb are neuronal phosphoproteins, which are supposed to play a role in the short-term regulation of neurotransmitt er release. Besides a high degree of homology among the four synapsin subtypes, there are structural differences in the 3' end of their codi ng region. Here we present the first extensive study of the expression of their gene transcripts by using in situ hybridization and northern blot analysis. Our results show regionally and temporally distinct ex pression patterns of synapsin Ia, Ib, IIa, and Ilb, which suggests dif ferent functional properties of the four synapsin subtypes. There was no specific messenger RNA (mRNA) expression of synapsin IIb in most br ain regions apart from the cerebellum, suggesting a minor functional r ole of this synapsin subtype. Synapsin Ia, Ib, and IIa mRNA were expre ssed earlier in ontogenetically older brain regions such as the pirifo rm cortex, the thalamus, and the hippocampus and later in ontogenetica lly younger areas such as the neocortex and the cerebellum. Owing to t he distinct expression pattern of the synapsin subtypes, we suppose th at the synapsins might be essential for the underlying molecular mecha nism of pattern formation and plasticity in distinct brain regions dur ing different states of rat brain development.