Fibroblast Growth Factor 2-Mediated Regulation of Neuronal Exosome Release Depends on VAMP3/Cellubrevin in Hippocampal Neurons

Extracellular vesicles (EVs) are endogenous membrane-derived vesicles that shuttle bioactive molecules between glia and neurons, thereby promoting neuronal survival and plasticity in the central nervous system (CNS) and contributing to neurodegenerative conditions. Although EVs hold great potential as CNS theranostic nanocarriers, the specific molecular factors that regulate neuronal EV uptake and release are currently unknown. A combination of patch-clamp electrophysiology and pH-sensitive dye imaging is used to examine stimulus-evoked EV release in individual neurons in real time. Whereas spontaneous electrical activity and the application of a high-frequency stimulus induce a slow and prolonged fusion of multivesicular bodies (MVBs) with the plasma membrane (PM) in a subset of cells, the neurotrophic factor basic fibroblast growth factor (bFGF) greatly increases the rate of stimulus-evoked MVB-PM fusion events and, consequently, the abundance of EVs in the culture medium. Proteomic analysis of neuronal EVs demonstrates bFGF increases the abundance of the v-SNARE vesicle-associated membrane protein 3 (VAMP3, cellubrevin) on EVs. Conversely, knocking-down VAMP3 in cultured neurons attenuates the effect of bFGF on EV release. The results determine the temporal characteristics of MVB-PM fusion in hippocampal neurons and reveal a new function for bFGF signaling in controlling neuronal EV release.

Quantitative topographical electroencephalographic analysis after intravenous clonidine in healthy male volunteers

We used quantitative topographical electroencephalography (EEG) to determine the time course of changes in brain electrical activity after clonidine infusion. Twenty healthy male volunteers (aged 24 +/- 5 yr) were included in the randomized, double-blind, placebo-controlled (Group 1, placebo, n = 10; Group 2, 2.0 micrograms/kg clonidine, n = 10) study. EEG (17 electrodes, common average reference, fast Fourier transformation, band pass 0.4-35.0 Hz) output was recorded until 145 min after drug infusion. Subjects were intermittently stimulated by verbal commands. Clonidine-related changes resulted in attenuation of the physiological alpha fluctuations seen in untreated subjects and were most pronounced at parietooccipital (P4, O2) recording sites. This was associated with initial maximal increases in slow wave activity (delta) almost uniformly distributed over the whole cortex, restricting with time to occipital regions (O2). The EEG mapping technique may provide more specific information about clonidine-mediated sedative effects, indicating facilitations of EEG patterns that are not homogeneously distributed. These EEG changes cannot be explained by physiologic changes in vigilance or by normal sleep stages because they were not observed after placebo. EEG effects seem to be unrelated to changes in hemodynamics.

IMPLICATIONS

In healthy volunteers, placebo-controlled signal changes in the electroencephalogram were evaluated to quantify sedative drug effects after intravenous application of clonidine. A multichannel recording system and electroencephalogram mapping technique indicate fluctuations of electroencephalogram patterns that are not homogeneously distributed over the cortex associated with sedation.