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Temporal lobe epilepsy (TLE) often becomes refractory, and patients with TLE show a high incidence of psychiatric symptoms, including anxiety and depression. Therefore, it is necessary to identify molecules that were previously unknown to contribute to epilepsy and its associated disorders. We previously found that the sialyltransferase ST3Gal IV is upregulated within the neural circuits through which amygdalakindling stimulation propagates epileptic seizures. In contrast, this study demonstrated that kindling stimulation failed to evoke epileptic seizures in ST3Gal IV-deficient mice. Furthermore, approximately 80% of these mice failed to show tonic-clonic seizures with stimulation, whereas all littermate wild-type mice showed tonic-clonic seizures. This indicates that the loss of ST3Gal IV does not cause TLE in mice. Meanwhile, ST3Gal IVdeficient mice exhibited decreased acclimation in the open field test, increased immobility in the forced swim test, enhanced freezing during delay auditory fear conditioning, and sleep disturbances. Thus, the loss of ST3Gal IV modulates anxietyrelated behaviors. These findings indicate that ST3Gal IV is a key molecule in the mechanisms underlying anxiety - a side effect of TLE - and may therefore also be an effective target for treating epilepsy, acting through the same circuits. [ABSTRACT FROM AUTHOR]

Deletion of cellular isoform of prion protein (PrPC) increases neuronal predisposition to damage by modulating apoptosis and the negative consequences of oxidative stress. In vivo studies have demonstrated that PrPC-deficient mice are more prone to seizure, depression, and induction of epilepsy and experience extensive cerebral damage following ischemic challenge or viral infection. In addition, adenovirus-mediated overexpression of PrPC reduces brain damage in rat models of cerebral ischemia. In experimental autoimmune encephalomyelitis, PrPC-deficient mice reportedly have a more aggressive disease onset and less clinical improvement during the chronic phase than wild-type mice mice. In mice given oral dextran sulfate, PrPC has a potential protective role against inflammatory bowel disease. PrPC-deficient mice demonstrate significantly greater increases in blood glucose concentrations after intraperitoneal injection of glucose than wild-type mice. Further in vivo challenges to PrP gene-deficient models and conditional knockout models with siRNA and in vivo administration of PrP-ligating agents may assist in refining knowledge of the lymphoid function of PrPC and predicting the effects of anti-PrP treatment on the immune system. Together, these findings indicate that PrPC may have multiple neuroprotective and anti-inflammatory roles, which explains why this protein is so widely expressed. [ABSTRACT FROM AUTHOR]

ABSTRACT Limited information is available about conformational differences between the abnormal isoform of prion protein (PrPSc) and cellular prion protein (PrPC) under native conditions. To clarify conformational differences between these two isoforms, PrP-deficient mice were immunized with brain homogenates of normal and scrapie-infected animals. All mice generated anti-PrP antibodies. Peptide array analysis of these serum samples revealed a distinctive epitope of PrPSc consisting of QGSPGGN (PrP41-47) at the N-terminus. This study demonstrated a conformational dissimilarity at the N-terminus between PrPSc and PrPC, a finding that may provide novel information about conformational features of PrPSc. [ABSTRACT FROM AUTHOR]

The development of topographic maps of the sensory periphery is sensitive to the disruption of adenylate cyclase 1 (AC1) signaling. AC1 catalyzes the production of cAMP in a Ca2+/calmodulin-dependent manner, and AC1 mutant mice (AC1−/−) have disordered visual and somatotopic maps. However, the broad expression of AC1 in the brain and the promiscuous nature of cAMP signaling have frustrated attempts to determine the underlying mechanism of AC1-dependent map development. In the mammalian visual system, the initial coarse targeting of retinal ganglion cell (RGC) projections to the superior colliculus (SC) and lateral geniculate nucleus (LGN) is guided by molecular cues, and the subsequent refinement of these crude projections occurs via an activity-dependent process that depends on spontaneous retinal waves. Here, we show that AC1−/− mice have normal retinal waves but disrupted map refinement. We demonstrate that AC1 is required for the emergence of dense and focused termination zones and elimination of inaccurately targeted collaterals at the level of individual retinofugal arbors. Conditional deletion of AC1 in the retina recapitulates map defects, indicating that the locus of map disruptions in the SC and dorsal LGN of AC1−/− mice is presynaptic. Finally, map defects in mice without AC1 and disrupted retinal waves (AC1−/−;β2−/− double KO mice) are no worse than those in mice lacking only β2−/−, but loss of AC1 occludes map recovery in β2−/− mice during the second postnatal week. These results suggest that AC1 in RGC axons mediates the development of retinotopy and eye-specific segregation in the SC and dorsal LGN. J. Comp. Neurol. 520:1562-1583, 2012. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

J. Neurochem. (2010) 112, 1035–1044. To identify a novel regulatory factor involved in brain development or synaptic plasticity, we applied the differential display PCR method to mRNA samples from NMDA-stimulated and un-stimulated neocortical cultures. Among 64 cDNA clones isolated, eight clones were novel genes and one of them encodes a novel zinc-finger protein, HIT-4, which is 317 amino acid residues (36–38 kDa) in length and contains seven C2H2 zinc-finger motifs. Rat HIT-4 cDNA exhibits strong homology to human ZNF597 (57% amino acid identity and 72% homology) and identity to rat ZNF597 at the carboxyl region. Furthermore, genomic alignment of HIT-4 cDNA indicates that the alternative use of distinct promoters and exons produces HIT-4 and ZNF597 mRNAs. Northern blotting revealed that HIT-4 mRNA (∼6 kb) is expressed in various tissues such as the lung, heart, and liver, but enriched in the brain, while ZNF597 mRNA (∼1.5 kb) is found only in the testis. To evaluate biological roles of HIT-4/ZNF597, targeted mutagenesis of this gene was performed in mice. Homozygous (−/−) mutation was embryonic lethal, ceasing embryonic organization before cardiogenesis at embryonic day 7.5. Heterozygous (+/−) mice were able to survive but showing cell degeneration and vacuolization of the striatum, cingulate cortex, and their surrounding white matter. These results reveal novel biological and pathological roles of HIT-4 in brain development and/or maintenance. [ABSTRACT FROM AUTHOR]

NR3B is a modulatory subunit of the NMDA receptor, abundantly expressed in both cranial and spinal somatic motoneurons and at lower levels in other regions of the brain as well. Recently, we found the human NR3B gene ( GRIN3B) to be highly genetically heterogeneous, and that ∼ 10% of the normal European-American population lacks NR3B due to homozygous occurrence of a null allele in the gene. Therefore, it is especially important to understand the phenotypic consequences of the genetic loss of NR3B in both humans and animal models. We here provide results of behavioral analysis of mice genetically lacking NR3B, which is an ideal animal model due to homogeneity in genetic and environmental background. The NR3B–/– mice are viable and fertile. Consistent with the expression of NR3B in somatic motoneurons, the NR3B–/– mice showed a moderate but significant impairment in motor learning or coordination, and decreased activity in their home cages. Remarkably, the NR3B–/– mice showed a highly increased social interaction with their familiar cage mates in their home cage but moderately increased anxiety-like behaviour and decreased social interaction in a novel environment, consistent with the inhibitory role of NR3B on the functions of NMDA receptors. This work is the first reporting of the functional significance of NR3B in vivo and may give insight into the contribution of genetic variability of NR3B in the phenotypic heterogeneity among human population. [ABSTRACT FROM AUTHOR]

Matrix metalloproteinases (MMPs) and its inhibitors (TIMPs) function to remodel the pericellular environment. We have demonstrated that methamphetamine (METH)-induced behavioral sensitization and reward were markedly attenuated in MMP-2- and MMP-9 deficient [MMP-2-(−/−) and MMP-9-(−/−)] mice compared with those in wild-type mice, suggesting that METH-induced expression of MMP-2 and MMP-9 in the brain plays a role in the development of METH-induced sensitization and reward. In the present study, we investigated the changes in TIMP-2 expression in the brain after repeated METH treatment. Furthermore, we studied a role of MMP/TIMP system in METH-induced behavioral changes and dopamine neurotransmission. Repeated METH treatment induced behavioral sensitization, which was accompanied by an increase in TIMP-2 expression. Antisense TIMP-2 oligonucleotide (TIMP-AS) treatment enhanced the sensitization, which was associated with the potentiation of METH-induced dopamine release in the nucleus accumbens (NAc). On the other hand, MMP-2/-9 inhibitors blocked the METH-induced behavioral sensitization and conditioned place preference, a measure of the rewarding effect, and reduced the METH-increased dopamine release in the NAc. Dopamine receptor agonist-stimulated [35S]GTPγS binding was reduced in the frontal cortex of sensitized rats. TIMP-AS treatment potentiated, while MMP-2/-9 inhibitor attenuated, the reduction of dopamine D2 receptor agonist-stimulated [35S]GTPγS binding. Repeated METH treatment also reduced dopamine D2 receptor agonist-stimulated [35S]GTPγS binding in wild-type mice, but such changes were significantly attenuated in MMP-2-(−/−) and MMP-9-(−/−) mice. These results suggest that the MMP/TIMP system is involved in METH-induced behavioral sensitization and reward, by regulating dopamine release and receptor signaling. [ABSTRACT FROM AUTHOR]

Matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) function to remodel the pericellular environment. Their activation and regulation are associated with synaptic physiology and pathology. Here, we investigated whether MMP-2 and MMP-9 are involved in the rewarding effects of and sensitization to methamphetamine (METH) in animals, in which the remodelling of neural circuits may play a crucial role. Repeated METH treatment induced behavioural sensitization, which was accompanied by an increase in MMP-2 and MMP-9 activity in the brain. In MMP-2- and MMP-9-deficient mice [MMP-2-(–/–) and MMP-9-(–/–)], METH-induced behavioural sensitization and conditioned place preference, a measure of the rewarding effect, as well as METH-increased dopamine release in the nucleus accumbens (NAc) were attenuated compared with those in wild-type mice. In contrast, infusion of purified human MMP-2 into the NAc significantly potentiated the METH-increased dopamine release. The [3H]dopamine uptake into striatal synaptosomes was reduced in wild-type mice after repeated METH treatment, but METH-induced changes in [3H]dopamine uptake were significantly attenuated in MMP-2-(–/–) and MMP-9-(–/–) mice. These results suggest that both MMP-2 and MMP-9 play a crucial role in METH-induced behavioural sensitization and reward by regulating METH-induced dopamine release and uptake in the NAc. [ABSTRACT FROM AUTHOR]

S100B is a calcium-binding protein predominantly expressed in astrocytes. Previous studies using gene-manipulated animals have suggested that the protein has a role in synaptic plasticity and learning. In order to assess the physiological roles of the protein in active neural circuitry, we recorded spontaneous neural activities from various layers of the neocortex and hippocampus in urethane-anesthetized S100B knockout (KO) and wildtype (WT) control mice. Typical local field oscillation patterns including the slow (0.5–2 Hz) oscillations in the neocortex, theta (3–8 Hz) and sharp wave-associated ripple (120–180 Hz) oscillations in the hippocampus were observed in both genotypes. Comparisons of the frequency, power and peak amplitude have shown that these oscillatory patterns were virtually indistinguishable between WT and KO. When seizure was induced by intraperitoneal injection of kainic acid, a difference between WT and KO appeared in the CA1 radiatum local field potential pattern, where seizure events were characterized by prominent appearance of hyper-synchronous gamma band (30–80 Hz) activity. Although both genotypes developed seizures within 40 min, the gamma amplitude was significantly smaller during the development of seizures in KO mice. Our results suggest that deficiency of S100B does not have a profound impact on spontaneous neural activity in normal conditions. However, when neural activity was sufficiently raised, activation of S100B-related pathways may take effect, resulting in modulation of neural activities. [ABSTRACT FROM AUTHOR]

Synaptotagmin-like protein (Slp) 2-a is a putative Rab27A/B-effector protein and is implicated in intracellular membrane transport. However, the precise tissue distribution of Slp2-a protein and its functions remain largely unknown. In this study we used a specific anti-Slp2-a antibody to investigate the tissue distribution of Slp2-a in mice and found that Slp2-a is most abundantly expressed in mouse stomach. Co-immunoprecipitation experiments indicated that Slp2-a interacts with Rab27A/B in vivo. We also discovered that Slp2-a and Rab27A/B are predominantly localized at the apical region of gastric-surface mucous cells, where mucus granules are accumulated. Analysis of Slp2-a mutant mice generated by homologous recombination showed a reduced number of mucus granules, a deficiency of granule docking with the apical plasma membrane in the gastric-surface mucous cells and reduction of mucus secretion by Slp2-a-deficient gastric primary cells. Based on these results, we propose that Slp2-a is part of the mucin secretory machinery in surface mucous cells of mouse stomach. [ABSTRACT FROM AUTHOR]

Abstract Background: Glial fibrillary acidic protein (GFAP) is the principal component of intermediate filaments (IFs) in mature astrocytes in the central nervous system (CNS). Like other IF proteins, GFAP has multiple phosphorylation sites in the N-terminal head domain. The distribution of phospho-GFAP in vivo has not been elucidated. Results: We generated Gfap hwt knock-in mice, in which the coding region for the head domain of GFAP is replaced with the corresponding human sequence. In combination with a series of monoclonal antibodies (mAbs) reactive to human phospho-GFAP, we visualized the distribution of phospho-GFAP in vivo in mice. GFAP phosphorylated at Thr7, Ser8 and/or Ser13 increased postnatally in the CNS of these mice. Limited populations of GFAP-positive astrocytes were labelled with anti-phospho-GFAP mAbs in most brain areas, whereas almost all the astrocytes in the optic nerve and spinal cord were labelled. Astrocytes in the subventricular zone and rostral migratory stream preferentially contained phospho-GFAP. In a cold injury model of the cerebral cortex, we detected phospho-GFAP in reactive astrocytes at 2–3 weeks after the injury. Conclusions: Phospho-GFAP provides a molecular marker indicating the heterogeneity of astrocytes, and Gfaphwt knock-in mice will aid in monitoring intracellular conditions of astrocytes, under various conditions. Our results suggest that the phosphorylation of GFAP plays a role in non-dividing astrocytes in vivo. [ABSTRACT FROM AUTHOR]

Abstract 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. [ABSTRACT FROM AUTHOR]

Abstract: The mature form of Alzheimer's β-amyloid precursor protein (APP) is phosphorylated specifically at Thr668 in neurons. In mature neurons, phosphorylated APP is detected in neurites, with dephosphorylated APP being found mostly in the cell body. In vitro, active cyclin-dependent kinase 5 (Cdk5) phosphorylated the cytoplasmic domain of APP at Thr668. Treatment of mature neurons with an antisense oligonucleotide to Cdk5 suppressed Cdk5 expression and significantly diminished the level of phosphorylated APP. The expression of APP was unaffected in antisense-treated neurons. These results indicate that in neurons APP is phosphorylated by Cdk5, and that this may play a role in its localization. [ABSTRACT FROM AUTHOR]

KKIAMRE is a serine/threonine protein kinase whose transcripts increase in the deep cerebellar nuclei of the rabbit after eyeblink conditioning, a model of associative learning and memory. We here characterized the expression, isoforms, and promoters of murine KKIAMRE gene. The expression of KKIAMRE was detected, by in situ hybridization and immunohistochemistry, in neurons in various brain regions including deep cerebellar nuclei. The gene spans ...40 kb and consists of 15 exons. Analysis of cDNA clones revealed multiple variants, having diversity in the putative carboxy-terminal regulatory domain, generated by alternative splicing and intraexonal termination. Furthermore, they had alternative 59 noncoding sequences. Primer extension, RNase protection, and transient expression assays revealed that two alternative promoters linked to distinct noncoding exons direct the expression of KKIAMRE. The gene was mapped on chromosomes 5 and 4 in mouse and human, respectively. [ABSTRACT FROM AUTHOR]

Abstract Doc2α is a synaptic vesicle-associated Ca2 + -binding protein. To study the role of Doc2α in synaptic transmission and modulation, we generated homozygous null Doc2α mutant mice. In the CA1 region of hippocampal slices in the mutant mice, excitatory synaptic responses evoked with prolonged 5 Hz stimulation showed a significantly larger frequency facilitation followed by a steeper depression than those in wild-type mice, whereas there was no difference in synaptic transmission at lower frequencies or in paired-pulse facilitation. These results suggest that Doc2α regulates synaptic transmission when high Ca2 + concentrations in the presynaptic terminal are sustained. Furthermore, the mutant mice showed impairment in long-term potentiation and passive avoidance task. Thus, Doc2α may regulate transmitter release during repetitive synaptic activation, thereby contributing to memory formation. [ABSTRACT FROM AUTHOR]

The tumour cells from 23 adult lymphosarcoma cattle were transplanted into 78 athymic mice; tumour growth was seen in two out of four of the mice transplanted with tumour cells from one of the leukaemic cattle. These mouse tumour cells were passaged in in vitro culture and in nude mice, and continuous cell lines were established. These cell lines were called BLSC-KU1 and BLST-KU1, respectively. At present, BLSC-KU1 has been maintained for 90 months. The following results were obtained using these established cell lines. 1. Morphological observations showed lymphoblastic cells. 2. Bovine leukaemia virus (BLV) particles and BLV antigen were both negative. 3. Cell surface immunoglobulin was positive. 4. Erythrocyte-antibody rosette and erythrocyte-antibody complement rosette formation were positive. 5. More than 85% of the cells reacted to anti-bovine thymocyte serum, but alpha-naphthyl acetate esterase staining and erythrocyte rosette formation were negative. 6. Anti-BLSC-KU1 antiserum showed a positive reaction with more than 90% of the BLSC-KU1 and BLST-KU1 cells, but did not react with the tumour cells of other enzootic bovine leukosis and sporadic leukosis cattle. Zusammenfassung Etablierung einer fortlaufenden Zellinie aus leukämischen Rindern Die Tumorzellen von 23 Rindern mit ausgereiften Lymphosarkomen wurden auf 78 thymuslose Mäuse transplantiert. Tumorwachstum konnte bei 2 von 4 mit Tumorzellen eines bestimmten leukämischen Rindes inokulierten Mäusen beobachter werden. Diese Maus-übertragenen Tumorzellen wurden in vitro und in Nacktmäusen weitergezüchtet, und eine fortlaufende Zellkultur wurde etabliert. Diese Zellinien wurden BLSC-KU1 und BLST-KU1 genannt. Bis zum jetzigen Zeitpunkt wurde die Linie BLSC-KU1 über 90 Monate kultiviert. Folgende Ergebnisse konnten mit den Zellinien erarbeitet werden: 1. Morphologische Studien zeigten lymphoblastoide Zellen. 2. Untersuchungen auf bovine Leukämie-Viruspartikel BLV und BLV-Antigen verliefen in beiden Fällen negativ. 3. Der Nachweis von zelloberflächen-assoziiertem Immunoglobulin war positiv. 4. Die Erythrozyten/Antikörper- und die Erythrozyten/Antikörper/Komplement-Rosettenbildung zeigten positive Ergebnisse. 5. Mehr als 85% der Zellen reagierten mit einem Anti-Rind-Thymozyten-Serum, jedoch blieben die alpha-naphthylacetat-Esterase-Färbung und eine Rosettenbildung mit Erythrozyten negativ. 6. Ein Anti-BLSC-KU1-Serum zeigte eine positive Reaktion mit mehr als 90% der BLSC-KU1 und BLST-KU1 Zellen, es reagierte aber nicht mit Tumorzellen anderer sporadisch oder enzootisch vorkommender Fälle boviner Leukose. [ABSTRACT FROM AUTHOR]

Abstract Among the subtypes of the Ca2+ -dependent protein kinase C (PKC), which play a crucial role in long-term depression (LTD), both α and γ are expressed in the cerebellar floccular Purkinje cells. To reveal the functional differences of PKC subtypes, we examined the adaptability of ocular reflexes of PKCγ mutant mice, which show mild ataxia and normal LTD. In mutant mice, gains of the horizontal optokinetic eye response (HOKR) were reduced. Adaptation of the HOKR was not affected but its retinal slip dependency was altered in mutant mice. Sustained 1-h sinusoidal screen oscillation, which induced a relatively large amount of retinal slips in both mutant and wild-type mice, increased the HOKR gain in wild-type mice but not in mutant mice. In contrast, exposure to 1 h of sustained slower screen oscillations, which induced relatively small retinal slips in mutant and wild-type mice, increased the HOKR gain in both mutant and wild-type mice. Adaptation of the HOKR of the mutant mice to slow screen oscillation and those of wild-type mice to fast and slow screen oscillations were all abolished by local applications of a PKC inhibitor (chelerythrine) within the flocculi. Electrophysiological and anatomical studies showed no appreciable changes in the sources and magnitudes of climbing fibre inputs, which mediate retinal slip signals to the flocculus in the mutant mice. These results suggest that PKCγ has a modulatory role in determining retinal slip dependency, and other PKC subtypes, e.g. PKCα, may play a crucial role in the adaptation of the HOKR. [ABSTRACT FROM AUTHOR]

Previous studies have shown that cellular prion protein (PrP(C)) plays anti-apoptotic and antioxidative role against cell death induced by serum-deprivation (SDP) in an immortalized prion protein gene-deficient neuronal cell line derived from Rikn prion protein (PrP) gene-deficient (Prnp(-/-)) mice, which ectopically produce excess Doppel (Dpl) (PrP-like glycoprotein). To investigate whether PrP(C) inhibits apoptotic neuronal cell death without Dpl, an immortalized cell line was established from the brain of ZrchI Prnp(-/-) mice, which do not show ectopic expression of Dpl. The results using a ZrchI neuronal Prnp(-/-) cell line (NpL2) showed that PrP(C) potently inhibited SDP-induced apoptotic cell death. Furthermore, PrP(C) expression enhanced the superoxide dismutase (SOD) activity in NpL2 cells. These results indicate that Dpl production did not affect anti-apoptotic and anti-oxidative functions of PrP, suggesting that PrP(C) may be directly correlated with protection against oxidative stress.

Our previous studies have shown an essential role played by the octapeptide repeat region (OR) and the N-terminal half of hydrophobic region (HR) in the anti-apoptotic activity of prion protein (PrP). As PrP-like protein Doppel (Dpl), which structurally resembles an N-terminally truncated PrP, did not show any anti-apoptotic activity, we examined apoptosis of HpL3-4 cells expressing Dpl fused to various lengths of the N-terminal region of PrP to investigate whether the PrP/Dpl fusion proteins retain anti-apoptotic function. HpL3-4 cells expressing Dpl fused to PrP(1-124) with the OR and N-terminal half of HR of PrP showed anti-apoptotic function, whereas Dpl fused to PrP(1-95) with OR did not rescue cells from apoptotic cell death induced by serum deprivation. These results indicate that the OR and N-terminal half of HR of PrP retains anti-apoptotic activity similar to full-length PrP.

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.