Brain‐Derived Neurotrophic Factor Increases the Stimulation‐Evoked Release of Glutamate and the Levels of Exocytosis‐Associated Proteins in Cultured Cortical Neurons from Embryonic Rats

Abstract

Differentiation and survival of neurons induced by neurotrophins have been widely investigated, but little has been reported about the long-term effect of brainderived neurotrophic factor (BDNF) on synaptic transmission. Among many steps of neurotransmission, one important step is regulated release of transmitters. Therefore, the release of glutamate and GABA from cortical neurons cultured for several days with or without BDNF was measured by an HPLC-fluorescence method. Although BDNF had little effect on the basal release of glutamate, high K + -evoked release was greatly increased by BDNF. BDNF also tended to increase evoked release of GABA. Recently, several proteins involved in the step of "regulated release" have been identified. Thus, the effect of BDNF on the levels of these proteins was then investigated. Neurons were cultivated with or without BDNF, collected, and electrophoresed for western blotting. BDNF increased levels of synaptotagmin, synaptobrevin, synaptophysin, and rab3A, which were known as vesicle protein. Levels of syntaxin, SNAP-25, and /3-SNAP were also increased by BDNF. In addition, the numbers of cored and clear vesicles in nerve terminals or varicosities were also increased by BDNF. These results raise the possibility that BDNF increases regulated release of neurotransmitters through the up-regulation of secretory mechanisms. Key Words: Brain-derived neurotrophic factor-Neurotrophin-3-Neurotrophin-Exocytosis-Synaptic vesicle-Transmitter release.

Neurotrophin signaling among neurons and glia during formation of tripartite synapses

“…BDNF and NT 3 treatment in E16 dissociated and P7 slice hippocampal cultures results in an increase in the number of synaptic vesicles docked at active zones (Collin et al, 2001;Tyler and Pozzo-Miller, 2001). Consistent with these observations, several groups report that BDNF treatment of hippocampal and cortical neuronal cultures increase synaptobrevin expression (Takei et al, 1997;Tartaglia et al, 2001;Yamada et al, 2002). In accordance with the effects of exogenous neurotrophins, mice that are deficient in either BDNF or TrkB exhibit marked reductions in the total number of docked vesicles at hippocampal synapses and a redistribution of docked vesicles to areas far from the active zone in the cerebellar synapses (Martinez et al, 1998;Pozzo-Miller et al, 1999;.…”

Environmental enrichment reduces the mnemonic and neural benefits of estrogen

“…Thus, the 3-4-month estrogen deprivation in our VEH-treated mice may have diminished the response of BDNF to environmental stimuli. Interestingly, BDNF has previously been shown to promote presynaptic vesicle docking and increase the amount of synaptophysin per neuron (Lu and Chow, 1999;Pozzo-Miller et al, 1999a;Takei et al, 1997). Therefore, it is surprising that our enrichmentinduced increases in synaptophysin did not positively correlate with changes in BDNF levels.…”

Transforming growth factor alpha attenuates the functional expression of AMPA receptors in cortical GABAergic neurons

“…For example, BDNF promotes phenotypic maturation of neocortical GABAergic neurons (Ip et al, 1993;Nawa et al, 1993;Croll et al, 1994;Marty et al, 1996;Reibel et al, 2000;Nagano et al, 2003). Exogenous and endogenous BDNF acts on developing GABAergic neurons to enhance the expression of glutamic acid decarboxylase (GAD), presynaptic proteins, and AMPA-type glutamate receptors as well as morphological differentiation (Mizuno et al, 1994;Jones et al, 1994;Takei et al, 1997;Narisawa-Saito et al, 1999a;Rutherford et al, 1998;Bolton et al, 2000). Gene manipulation studies have confirmed the facilitatory effects of BDNF on the neocortical GABAergic inhibition as well (Jones et al, 1994;Huang et al, 1999;Gorski et al, 2003).…”