SUMMARY NR3A is the only NMDA receptor (NMDAR) subunit that down-regulates sharply prior to the onset of sensitive periods for plasticity, yet the functional importance of this transient expression remains largely unknown. To investigate the possibility that removal/replacement of juvenile NR3A-containing NMDARs is involved in experience-driven synapse maturation, we used a reversible transgenic system that allowed persistent NR3A expression in the postnatal forebrain. We found that removal of NR3A is required to develop strong NMDAR currents, full expression of long-term synaptic plasticity, a mature synaptic organization characterized by more synapses and larger postsynaptic densities, and the ability to form long-term memories. Deficits associated with prolonged NR3A were reversible, as late-onset suppression of transgene expression rescued both the synaptic and memory impairments. Our results suggest that NR3A behaves as a molecular brake to prevent the premature strengthening and stabilization of excitatory synapses, and that NR3A removal might thereby initiate critical stages of synapse maturation during early postnatal neural development.

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GAGs coatings are performed using SH-SY5Y and CCF-STTG1 cell lines and with ATP and Ca(2+) . Results show full biocompatibility and a pronounced anti-inflammatory effect. This last characteristic becomes crucial if implanted in the body. These materials can be used for in vivo applications, as transistor or electrode for electrical recording and for all the possible situations when there is contact between electronic circuits and living tissues.

Genetically encoded fluorescent Ca2+ indicator proteins (FCIPs) are promising tools to study Ca2+ signaling in large assemblies of nerve cells. Currently, there are few examples of stable transgenic mouse lines that functionally express such sensors in well-defined neuronal cell populations. Here we report the generation and characterization of transgenic mice expressing an FCIP under the 5' regulatory sequences of the Kv3.1 potassium channel promoter. In the cerebellar cortex, expression was restricted to granule cells. We first demonstrated reliable measurements of Ca2+ transients from beams of parallel fibers and compared the FCIP signals with intrinsic autofluorescence signals. We demonstrate that, in a transgenic line that exhibits a high expression level of the FCIP, autofluorescence signals are negligible and stimulation-induced fluorescence transients represent FCIP signals. Using frontal cerebellar slices we imaged antidromic activation of granule cells following electrical stimulation of parallel fibers and orthodromic activation of beams of parallel fibers following electrical stimulation of granule cells. We found that paired pulse-induced presynaptic Ca2+ transients of parallel fibers are not affected by blockade of N-methyl-D-aspartate receptors.

During the last few years a variety of genetically encodable optical probes that monitor physiological parameters such as local pH, Ca2+, Cl-, or transmembrane voltage have been developed. These sensors are based on variants of green-fluorescent protein (GFP) and can be synthesized by mammalian cells after transfection with cDNA. To use these sensor proteins in intact brain tissue, specific promoters are needed that drive protein expression at a sufficiently high expression level in distinct neuronal subpopulations. Here we investigated whether the promoter sequence of a particular potassium channel may be useful for this purpose. We produced transgenic mouse lines carrying the gene for enhanced yellow-fluorescent protein (EYFP), a yellow-green pH- and Cl- sensitive variant of GFP, under control of the Kv3.1 K+ channel promoter (pKv3.1). Transgenic mouse lines displayed high levels of EYFP expression, identified by confocal microscopy, in adult cerebellar granule cells, interneurons of the cerebral cortex, and in neurons of hippocampus and thalamus. Furthermore, using living cerebellar slices we demonstrate that expression levels of EYFP are sufficient to report intracellular pH and Cl- concentration using imaging techniques and conditions analogous to those used with conventional ion-sensitive dyes. We conclude that transgenic mice expressing GFP-derived sensors under the control of cell-type specific promoters, provide a unique opportunity for functional characterization of defined subsets of neurons.