Until now, the only well documented, fast excitatory neurotransmitter in the brain has been glutamate. Although there is evidence for adenosine 5'-triphosphate (ATP) acting as a transmitter in the peripheral nervous system, suggestions for such a role in the central nervous system have so far not been supported by any direct evidence. Here we report the recording of evoked and miniature synaptic currents in the rat medial habenula. The fast rise time of the currents showed that they were mediated by a ligand-activated ion channel rather than a second messenger system, thus limiting the known transmitter candidates. Evidence was found for the presence on the cells of glutamate, gamma-aminobutyric acid, acetylcholine and ATP receptors, but not for 5-hydroxytryptamine (5HT3) or glycine receptors. The evoked currents were unaffected by blockers of glutamate, gamma-aminobutyric acid or acetylcholine receptors but were blocked by the ATP receptor-blocker, suramin and the desensitizing ATP receptor-agonist alpha,beta-methylene-ATP. Our evidence identifies for the first time synaptic currents in the brain, mediated directly by ATP receptors.

We provide microarray data comparing genome-wide differential expression and pathology throughout life in four lines of "amyloid" transgenic mice (mutant human APP, PSEN1, or APP/PSEN1) and "TAU" transgenic mice (mutant human MAPT gene). Microarray data were validated by qPCR and by comparison to human studies, including genome-wide association study (GWAS) hits. Immune gene expression correlated tightly with plaques whereas synaptic genes correlated negatively with neurofibrillary tangles. Network analysis of immune gene modules revealed six hub genes in hippocampus of amyloid mice, four in common with cortex. The hippocampal network in TAU mice was similar except that Trem2 had hub status only in amyloid mice. The cortical network of TAU mice was entirely different with more hub genes and few in common with the other networks, suggesting reasons for specificity of cortical dysfunction in FTDP17. This Resource opens up many areas for investigation. All data are available and searchable at http://www.mouseac.org.

BackgroundNeural stem cells (NSCs) are powerful research tools for the design and discovery of new approaches to neurodegenerative disease. Overexpression of the myc family transcription factors in human primary cells from developing cortex and mesencephalon has produced two stable multipotential NSC lines (ReNcell VM and CX) that can be continuously expanded in monolayer culture.ResultsIn the undifferentiated state, both ReNcell VM and CX are nestin positive and have resting membrane potentials of around -60 mV but do not display any voltage-activated conductances. As initially hypothesized, using standard methods (stdD) for differentiation, both cell lines can form neurons, astrocytes and oligodendrocytes according to immunohistological characteristics. However it became clear that this was not true for electrophysiological features which designate neurons, such as the firing of action potentials. We have thus developed a new differentiation protocol, designated 'pre-aggregation differentiation' (preD) which appears to favor development of electrophysiologically functional neurons and to lead to an increase in dopaminergic neurons in the ReNcell VM line. In contrast, the protocol used had little effect on the differentiation of ReNcell CX in which dopaminergic differentiation was not observed. Moreover, after a week of differentiation with the preD protocol, 100% of ReNcell VM featured TTX-sensitive Na+-channels and fired action potentials, compared to 25% after stdD. Currents via other voltage-gated channels did not appear to depend on the differentiation protocol. ReNcell CX did not display the same electrophysiological properties as the VM line, generating voltage-dependant K+ currents but no Na+ currents or action potentials under either stdD or preD differentiation.ConclusionThese data demonstrate that overexpression of myc in NSCs can be used to generate electrophysiologically active neurons in culture. Development of a functional neuronal phenotype may be dependent on parameters of isolation and differentiation of the cell lines, indicating that not all human NSCs are functionally equivalent.

Despite their wide use, the physiological relevance of organotypic slices remains controversial. Such cultures are prepared at 5 days postnatal. Although some local circuitry remains intact, they develop subsequently in isolation from the animal and hence without plasticity due to experience. Development of synaptic connectivity and morphology might be expected to proceed differently under these conditions than in a behaving animal. To address these questions, patch‐clamp techniques and confocal microscopy were used in the CA1 region of the rat hippocampus to compare acute slices from the third postnatal week with various stages of organotypic slices. Acute slices prepared at postnatal days (P) 14, 17 and 21 were found to be developmentally equivalent to organotypic slices cultured for 1, 2 and 3 weeks, respectively, in terms of development of synaptic transmission and dendritic morphology. The frequency of inhibitory and excitatory miniature synaptic currents increased in parallel. Development of dendritic length and primary branching as well as spine density and proportions of different spine types were also similar in both preparations, at these corresponding stages. The most notable difference between organotypic and acute slices was a four‐ to five‐fold increase in the absolute frequency of glutamatergic (but not GABAergic) miniature postsynaptic currents in organotypic slices. This was probably related to an increase in complexity of higher order dendritic branching in organotypic slices, as measured by fractal analysis, resulting in an increased total synapse number. Both increased excitatory miniature synaptic current frequency and dendritic complexity were already established during the first week in culture. The level of complexity then stayed constant in both preparations over subsequent stages, with synaptic frequency increasing in parallel. Thus, although connectivity was greater in organotypic slices, once this was established, development continued in both preparations at a remarkably similar rate. We conclude that, for the parameters studied, changes seem to be preprogrammed by 5 days and their subsequent development is largely independent of environment.