Synapsins as mediators of BDNF-enhanced neurotransmitter release

We examined enhancement of synaptic transmission by neurotrophins at the pr esynaptic level. In a synaptosomal preparation, brain-derived neurotrophic factor (BDNF) increased mitogen-activated protein (MAP) kinase-dependent sy napsin I phosphorylation and acutely facilitated evoked glutamate release. PD98059, used to inhibit MAP kinase activity, markedly decreased synapsin I phosphorylation and concomitantly reduced neurotransmitter release. The st imulation of glutamate release by BDNF was strongly attenuated in mice lack ing synapsin I and/or synapsin II. These results indicate at causal link of synapsin phosphorylation via BDNF, TrkB receptors and MAP kinase with down stream facilitation of neurotransmitter release.