Electroconvulsive shock reduces inositol 1,4,5-trisphosphate 3-kinase mRNA expression in rat dentate gyrus

PKA-dependent phosphorylation of IP3K-A at Ser119 regulates a binding affinity with EB3

Microtubule-associated end-binding protein 3 (EB3) accumulates asymmetrically at the tip-end of growing microtubules, providing a central platform for linking various cellular components. EB3 orchestrates microtubule dynamics and targeting, enabling diverse processes within neurons. Inositol 1, 4, 5-trisphosphate 3-kinase A (IP3K-A; also known as ITPKA) is a neuron-enriched protein that binds to microtubules by PKA-dependent manners. In this study, we found that IP3K-A binds to EB3 and their binding affinity is precisely regulated by protein kinase A (PKA)-dependent phosphorylation of IP3K-A at Ser119 (pSer119). We also revealed that the complex of IP3K-A and EB3 dissociates and reassociates rapidly during chemically induced LTP (cLTP) condition. This dynamic rearrangement of IP3K-A and EB3 complex will contribute remodeling of microtubule cytoskeleton allowing effective structural plasticity in response to synaptic stimulations.

Transgenic mice expressing yellow fluorescent protein under control of the human tyrosine hydroxylase promoter

Pathogenesis of Parkinson's disease and related catecholaminergic neurological disorders is closely associated with changes in the levels of tyrosine hydroxylase (TH). Therefore, investigation of the regulation of the TH gene system should assist in understanding the pathomechanisms involved in these neurological disorders. To identify regulatory domains that direct human TH expression in the central nervous system (CNS), we generated two transgenic mouse lines in which enhanced yellow fluorescent protein (EYFP) is expressed under the control of either 3.2-kb (hTHP-EYFP construct) human TH promoter or 3.2-kb promoter with 2-kb 3'-flanking regions (hTHP-ex3-EYFP construct) of the TH gene. In the adult transgenic mouse brain, the hTHP-EYFP construct directs neuron-specific EYFP expression in various CNS areas, such as olfactory bulb, striatum, interpeduncular nucleus, cerebral cortex, hippocampus, and particularly dentate gyrus. Although these EYFP-positive cells were identified as mature neurons, few EYFP-positive cells were TH-positive neurons. On the other hand, we could detect the EYFP mRNA expression in a subset of neurons in the olfactory bulb, midbrain, and cerebellum, in which expression of endogenous TH is enriched, with hTHP-ex3-EYFP transgenic mice. These results indicate that the 3.2-kb sequence upstream of the TH gene is not sufficient for proper expression and that the 2-kb sequence from the translation start site to exon 3 is necessary for expression of EYFP in a subset of catecholaminergic neurons.

Inositol 1,4,5-trisphosphate 3-kinase a functions as a scaffold for synaptic Rac signaling

Activity-dependent alterations of synaptic contacts are crucial for synaptic plasticity. The formation of new dendritic spines and synapses is known to require actin cytoskeletal reorganization specifically during neural activation phases. Yet the site-specific and time-dependent mechanisms modulating actin dynamics in mature neurons are not well understood. In this study, we show that actin dynamics in spines is regulated by a Rac anchoring and targeting function of inositol 1,4,5-trisphosphate 3-kinase A (IP(3)K-A), independent of its kinase activity. On neural activation, IP(3)K-A bound directly to activated Rac1 and recruited it to the actin cytoskeleton in the postsynaptic area. This focal targeting of activated Rac1 induced spine formation through actin dynamics downstream of Rac signaling. Consistent with the scaffolding role of IP(3)K-A, IP(3)K-A knock-out mice exhibited defects in accumulation of PAK1 by long-term potentiation-inducing stimulation. This deficiency resulted in a reduction in the reorganization of actin cytoskeletal structures in the synaptic area of dentate gyrus. Moreover, IP(3)K-A knock-out mice showed deficits of synaptic plasticity in perforant path and in hippocampal-dependent memory performances. These data support a novel model in which IP(3)K-A is critical for the spatial and temporal regulation of spine actin remodeling, synaptic plasticity, and learning and memory via an activity-dependent Rac scaffolding mechanism.

Regulation of AHI1 expression in adult rat brain: Implication in hypothalamic feeding control

Recent studies revealed that Abelson helper integration site 1 (AHI1) plays a role in brain development. However, little is known about the role of AHI1 in adult brain. To directly assess the role of AHI1 in the adult brain, we cloned full-length cDNA of rat AHI1 and observed prominent expression of AHI1 in the hypothalamus, which contributes mainly to the control of energy homeostasis. Furthermore, we demonstrated that food deprivation caused induction of AHI1 in the hypothalamus and subsequent re-feeding down-regulated AHI1 expression, suggesting the involvement of AHI1 in feeding control. Moreover, the expression of AHI1 was increased in serum-depleted Neuro2A cells and restored by subsequent insulin treatment. Furthermore, treatment in food-deprived rat with intraperitoneal glucose also reduced the increased AHI1 expression. These results demonstrate that AHI1 expression can be regulated through diet and suggest the novel role of AHI1 in feeding behavior.

Spatiotemporal expression pattern of non-clustered protocadherin family members in the developing rat brain

Protocadherins (PCDHs) consist of the largest subgroup of the cadherin superfamily, and most PCDHs are expressed dominantly in the CNS. Because PCDHs are involved in the homophilic cell-cell adhesion, PCDHs in the nervous system have been suggested to play roles in the formation and maintenance of the synaptic connections. Although many PCDHs (>50) are in tandem arranged as a cluster in a specific chromosome locus, there are also considerable numbers of non-clustered PCDH members (approximately 20). In this study, we examined the spatiotemporal distribution of mRNAs for 12 non-clustered PCDHs in rat brain using in situ hybridization. Some of them (PCDH1, PCDH7, PCDH9, PCDH10, PCDH11, PCDH17, and PCDH20) exhibited region-dependent expression pattern in the cerebral cortex during the early postnatal stage (P3), which is a critical period for the establishment of specific synaptic connections: PCDH7 and PCDH20 mRNAs were predominantly expressed in the somatosensory (parietal) and visual (occipital) cortices, whereas PCDH11 and PCDH17 mRNAs were preferentially expressed in the motor (forelimb and hindlimb areas) and auditory (temporal) cortices, and PCDH9 mRNA was highly expressed in the motor and main somatosensory cortices. These PCDHs were also expressed in the specific regions of the connecting thalamic nuclei. These cortical regionalization and thalamic nuclei-specificity appeared to be most distinct in P3 compared with those of embryonic and adult stages. Taken together, these results suggest that PCDHs may play specific roles in the establishment of selective synaptic connections of specific modality of cerebral cortex with other communicating brain regions such as the thalamus.

Identification and characterization of novel activity-dependent transcription factors in rat cortical neurons

Using gene chip analyses, we have identified novel neuronal activity-dependent genes. Application of 25 mM KCl to mature (14-day culture) rat cortical neurons resulted in more than 1.5-fold induction of 19 genes and reduction of 42 genes among 1200 neural genes. Changes in the overall gene expression profiles appeared to be related to the reduction of excitability and induction of cellular survival signals. Among the genes identified, three transcriptional modulators [encoding Cbp/p300-interacting transactivator with ED-rich tail 2 (CITED2), CCAAT/enhancer binding protein beta (C/EBPbeta) and neuronal orphan receptor-1, (NOR1)] were newly identified as activity-dependent transcription factors, and two of these (CITED2 and NOR1) were found to be influenced by electroconvulsive shock (ECS). NOR1 was induced in specific brain regions by behavioral activation, such as exposure to a novel environment. Because the brain regions that exhibited the induction of these newly identified neuronal activity-dependent transcriptional modulators were distinct from those showing the induction of previously identified activity-dependent genes such as c-fos, these genes might be useful markers for mapping neuronal activity in vivo.

Inhibition of rat brain inositol 1,4,5-trisphosphate 3-kinase A expression by kainic acid

Defects in intracellular calcium homeostasis may cause aberrant neuronal activation and subsequent neuronal death. Because inositol trisphosphate (IP(3)) regulates the release of calcium from the endoplasmic reticulum and the IP(3) kinase A isoform (IP(3)K-A) reduces intracellular IP(3), regulation of IP(3)K could be involved in neuronal activation and/or neuronal death. In this study, we found that kainic acid (KA) treatment in vitro and in vivo reduced the level of IP(3)K-A mRNA. Since KA treatment induces aberrant neuronal activation and neuronal death, we tested whether the reduction of IP(3)K-A mRNA was required for KA-induced neuronal death. Overexpression of adenovirus-derived IP(3)K-A failed to rescue neurons from KA-induced death. Because neuronal activation by KCl in vitro is sufficient to reduce IP(3)K-A expression, we conclude that the KA-derived reduction of IP(3)K-A expression is due to the aberrant neuronal activation, and the reduction in the IP3K-A mRNA level is not required for the toxic effect of KA.

Effect of thymosin β15 on the branching of developing neurons

The thymosin betas (Tbetas) are polypeptide regulators of actin dynamics that are critical for the growth and branching of neurites in developing neurons. We found that mRNAs for Tbeta4, Tbeta10, and Tbeta15 were highly expressed in the developing rat brain during neuritogenesis, supporting a role for the Tbetas in this process. Overexpression of the Tbetas increased the number of neurite branches per neuron in cultured hippocampal and cerebral cortex neurons, and Tbeta15 had the greatest effect. Actin binding activity appears to be essential for the branch-promoting activity of Tbetas because two mutants of Tbeta15 lacking monomeric actin binding activity failed to stimulate branch formation. We also found that transfection of siRNA against Tbeta15 reduced branching. Taken together, these data suggest that the three Tbetas, and especially Tbeta15, stimulate neurite branching during brain development.

Identification of novel electroconvulsive shock-induced and activity-dependent genes in the rat brain

Electroconvulsive shock (ECS) has been used as an effective treatment for patients suffering from major depression disorders and schizophrenia. However, the exact mechanisms underlying the action of ECS are poorly understood. Using high-density oligonucleotide microarrays, we identified 60 ECS-induced genes whose gene products are involved in the neuronal signaling, neuritogenesis and tissue remodeling. In situ hybridization and depolarization-dependent expression assay were performed to characterize 4 genes (lysyl oxidase, Ab1-046, SOX11, and T-type calcium channel 1G subunit) which have not yet been reported to be induced by ECS. Interestingly, the induction of these genes was observed mainly in the dentate gyrus of hippocampal formation and piriform cortex, where ECS-induced neural activation is highlighted, and depolarization of cultured cortical neurons also induced the expression of these genes. Taken together, our results suggest that therapeutic actions of ECS may be manifested by the activity-dependent induction of genes related to the plastic changes of the brain such as neuronal signaling neuritogenesis, and tissue remodeling.

Genetic interactions of DST1 in Saccharomyces cerevisiae suggest a role of TFIIS in the initiation-elongation transition

TFIIS promotes the intrinsic ability of RNA polymerase II to cleave the 3'-end of the newly synthesized RNA. This stimulatory activity of TFIIS, which is dependent upon Rpb9, facilitates the resumption of transcription elongation when the polymerase stalls or arrests. While TFIIS has a pronounced effect on transcription elongation in vitro, the deletion of DST1 has no major effect on cell viability. In this work we used a genetic approach to increase our knowledge of the role of TFIIS in vivo. We showed that: (1) dst1 and rpb9 mutants have a synthetic growth defective phenotype when combined with fyv4, gim5, htz1, yal011w, ybr231c, soh1, vps71, and vps72 mutants that is exacerbated during germination or at high salt concentrations; (2) TFIIS and Rpb9 are essential when the cells are challenged with microtubule-destabilizing drugs; (3) among the SDO (synthetic with Dst one), SOH1 shows the strongest genetic interaction with DST1; (4) the presence of multiple copies of TAF14, SUA7, GAL11, RTS1, and TYS1 alleviate the growth phenotype of dst1 soh1 mutants; and (5) SRB5 and SIN4 genetically interact with DST1. We propose that TFIIS is required under stress conditions and that TFIIS is important for the transition between initiation and elongation in vivo.

Spatial learning enhances the expression of inositol 1,4,5-trisphosphate 3-kinase A in the hippocampal formation of rat

Calcium-mediated signaling is crucial for the synaptic plasticity and long-term memory storage, which requires de novo protein synthesis. Inositol 1,4,5-trisphosphate 3-kinase A (IP(3)K-A) is an enzyme, which is involved in the maintenance of intracellular calcium homeostasis by converting inositol 1,4,5-trisphosphate (IP(3)) to inositol 1,3,4,5-tetrakisphosphate (IP(4)). Because IP(3)K-A is enriched in the dendritic spines of hippocampal neurons, it has been speculated that this enzyme is involved in the memory formation. In the present study, we demonstrated that the expression of IP(3)K-A is increased in the hippocampal formation of the rats during the Morris water maze training. Immunohistochemical analysis indicated the specific induction of IP(3)K-A protein in the hippocampal formation following 5-day water maze training. Furthermore, in situ hybridization histochemistry showed that the induction of IP(3)K-A mRNA in the hippocampal formation was observed on the first day of training, and the induced level of IP(3)K-A mRNA was maintained until the fifth day of training. These results suggest that IP(3)K-A plays a role in the processing of spatial memory, most likely by regulating the calcium signaling in the dendritic spines of hippocampal formation.

Altered neuronal nitric oxide synthase expression in the cerebellum of calcium channel mutant mice

Tottering, rolling Nagoya, and leaner mutant mice all exhibit cerebellar ataxia to varying degrees, from mild (tottering mice) to severe (leaner mice). Collectively, these mice are regarded as tottering locus mutants because each of these mutant mice expresses a different autosomal recessive mutation in the gene coding for the alpha(1A) calcium ion channel protein, which is the pore forming subunit for P/Q-type high voltage activated calcium ion channels. These mutant mice all exhibit varying degrees of cerebellar dysfunction and neuronal cell death. Nitric oxide (NO) is an important messenger molecule in the central nervous system, especially in the cerebellum, and it is produced via the enzyme, nitric oxide synthase (NOS). We investigated expression of neuronal-NOS (n-NOS) in the cerebella of all three mutant mice, as revealed by NADPH-diaphorase (NADPH-d) histochemical staining, quantitation of n-NOS protein using Western blotting and quantitation of n-NOS mRNA using in situ hybridization. The expression of n-NOS mRNA and protein as well as the NADPH-d histochemical reaction were elevated in tottering and rolling Nagoya cerebella. n-NOS mRNA and the NADPH-d histochemical reaction were decreased in the leaner cerebellum, but the leaner mouse n-NOS protein concentration was not significantly different compared to age- and gender-matched controls. These findings suggest that NO may act as an important mediator in the production of the neuropathology observed in these mutant mice.

Ontogeny and the possible function of a novel epidermal growth factor-like repeat domain-containing protein, NELL2, in the rat brain

In this study we investigated the mRNA expression of NELL2, a neural tissue-specific epidermal growth factor (EGF)-like repeat domain-containing protein, in the developing and adult rat CNS using in situ hybridization histochemistry and northern blot analysis. The possible candidates that interact with or be regulated by NELL2 were screened with a cDNA expression array in antisense (AS) NELL2 oligodeoxynucleotide (ODN)-injected rat hypothalami. NELL2 mRNA was detected as early as embryonic day 10, and was predominant in the CNS throughout the pre-natal stages. Its expression gradually increased during embryonic development and its strong expression was observed throughout the CNS until embryonic day 20. It was detected in the ventricular zone of the spinal cord, medulla and pons in 12-day-old-embryos, suggesting that NELL2 plays a role in the neurogenesis of these areas. After birth its expression gradually decreased, but high levels of expression could be observed in the tenia tecta, piriform cortex, hippocampus, dentate gyrus, cerebellar cortex, ambiguus nucleus, and inferior olivary nucleus of adult rat brains. The analysis of cDNA expression arrays revealed that the administration of AS NELL2 ODN markedly decreased the expression of several Ca2+-binding proteins and those involved in the transport and release of vesicles such as EF-hand Ca2+-binding protein p22 and rab7. This finding was confirmed by relative reverse transcription-polymerase chain reaction. The effect of NELL2 on synaptic vesicle content in median eminence (ME) nerve terminals was determined with synaptophysin levels as a marker protein in the AS NELL2 ODN-injected rat. It was significantly decreased by the AS ODN. These data suggest that NELL2 may play an important role in the development of the CNS as well as maintenance of neural functions, by regulating the intracellular machinery involving Ca2+ signaling, synaptic transport and/or release of vesicles.

Cloning and localization of rgpr85 encoding rat G-protein-coupled receptor

In an attempt to isolate genes involved in the brain development using ordered differential display PCR, we cloned rgpr85 which encodes rat G-protein-coupled receptor with high degree of identity to the amine-like neurotransmitter receptors. This gene was found to be localized at rat chromosome 4q21. In situ hybridization demonstrated that rgpr85 was predominantly expressed in the developing brain and spinal cord. Hybridization signal was especially abundant within the embryonic cortical plates where postmitotic cortical neurons are localized. In the cerebral cortex, the expression of rgpr85 was gradually decreased postnatally and became undetectable by P18. However, weak but significant expression of rgpr85 was maintained in the adult hippocampal formation, olfactory bulb, and cerebellum. Interestingly, rgpr85 expression was transiently induced in the adult hippocampal formation, piriform cortex, and amygdaloid complex by kainic acid (KA) treatment. Thus, dynamic regulation of rgpr85 expression suggests an importance of rgpr85-mediated signaling in the development of cerebral cortex and in the KA-induced responses in the adult brain.

The induction of BDNF and c-fos mRNA in the hippocampal formation after febrile seizures

In this study we investigated the expression of brain-derived neurotrophic factor (BDNF) and c-fos mRNA in the hippocampal formation after febrile seizures (FSs) with in situ hybridization histochemistry using riboprobes. The induction of BDNF mRNA was firstly observed in the dentate gyrus at 30 min after FSs. The expression in the dentate gyrus peaked at 3 h and returned to basal level at 24 h. It was also observed in the CA3 of hippocampus from 2 to 3 h. The induction of c-fos mRNA was observed in the dentate gyrus at 30 min and 1 h. These observations suggest that BDNF and c-fos are the genes whose expression can be altered by FSs and might be related to pathologic alterations after FSs.

Molecular cloning of neuronally expressed mouse betaPix isoforms

Pix, a Pak-interacting exchange factor, is known to be involved in the regulation of Cdc42/Rac GTPases and Pak kinase activity. In this study, we cloned the cDNAs encoding two betaPix isoforms from mouse brain cDNA library. Both of the cloned genes, designated betaPix-b and betaPix-c (GenBank Accession Nos. AF247654 and AF247655, respectively), have a novel insert region consisting of 59 amino acid residues. In betaPix-c, 75 amino acid residues are deleted in the proline-rich region at the carboxyl-terminus of betaPix. In situ hybridization studies with insert region-specific probe in rat embryo show that insert region-containing isoforms are expressed mainly in the central nervous system. Moreover, temporal expression pattern of isoforms is correlated with the active neurogenesis period in the cerebral cortex and cerebellum. These results strongly suggest that betaPix isoforms may play important roles in the cellular events required for brain development such as neuronal migration.

Hepatic expression, synthesis and secretion of a novel fibrinogen/angiopoietin-related protein that prevents endothelial-cell apoptosis

Using degenerate PCR we isolated a cDNA encoding a novel 406- and 410-amino acid protein from human and mouse embryonic cDNAs and have designated it 'hepatic fibrinogen/angiopoietin-related protein' (HFARP). The N-terminal and C-terminal portions of HFARP contain the characteristic coiled-coil domains and fibrinogen-like domains that are conserved in angiopoietins. In human and mouse tissues, HFARP mRNA is specifically expressed in the liver. HFARP mRNA and protein are mainly present in the hepatocytes. HFARP has a highly hydrophobic region at the N-terminus that is typical of a secretory signal sequence and one consensus glycosylation site. Recombinant HFARP expressed in COS-7 cells is secreted and glycosylated. HFARP protein is present not only in the hepatocytes, but also in the circulating blood. Recombinant HFARP acts as an apoptosis survival factor for vascular endothelial cells, but does not bind to Tie1 or Tie2 (endothelial-cell tyrosine kinase receptors). These results suggest that HFARP may exert a protective function on endothelial cells through an endocrine action.

Molecular cloning, expression, and characterization of angiopoietin-related protein. angiopoietin-related protein induces endothelial cell sprouting

Using degenerate polymerase chain reaction, we isolated a cDNA encoding a novel 493-amino acid protein from human and mouse adult heart cDNAs and have designated it angiopoietin-related protein-2 (ARP2). The NH(2)-terminal and COOH-terminal portions of ARP2 contain the characteristic coiled-coil domain and fibrinogen-like domain that are conserved in angiopoietins. ARP2 has two consensus glycosylation sites and a highly hydrophobic region at the NH(2) terminus that is typical of a secretory signal sequence. Recombinant ARP2 expressed in COS cells is secreted and glycosylated. In human adult tissues, ARP2 mRNA is most abundant in heart, small intestine, spleen, and stomach. In rat embryos, ARP2 mRNA is most abundant in the blood vessels and skeletal muscles. Endothelial and vascular smooth muscle cells also contain ARP2 mRNA. Recombinant ARP2 protein induces sprouting in vascular endothelial cells but does not bind to the Tie1 or Tie2 receptor. These results suggest that ARP2 may exert a function on endothelial cells through autocrine or paracrine action.

MK-801, a non-competitive NMDA receptor antagonist, prevents postischemic decrease of inositol 1,4,5-trisphosphate receptor mRNA expression in mongolian gerbil brain

Changes of inositol 1,4,5-trisphosphate receptor (IP3R) mRNA expression after transient brain ischemia and the effect of MK-801, a non-competitive N-methyl-D-aspartic acid (NMDA) receptor antagonist, on the IP3R mRNA expression was studied in mongolian gerbil brain by in situ hybridization. Transient ischemia was induced by ligating left common carotid artery for 10 min, and the animals were allowed recovery from 15 min to 24 h. MK-801 was introduced intraperitoneally 30 min before ischemia. IP3R mRNA expression was decreased in dentate gyrus and hippocampus from 90 min until 24 h after ischemia. MK-801 pretreatment prevented the change of IP3R mRNA expression after ischemia. These results suggest that IP3R mRNA expression in ischemia may be related with NMDA receptor.

Cloning of the genes encoding mouse cardiac and skeletal calsequestrins: expression pattern during embryogenesis

Calsequestrin is a low-affinity and high-capacity calcium-binding protein in the sarcoplasmic reticulum (SR). In the present study, we have cloned and sequenced mouse cardiac and skeletal calsequestrin cDNAs. The deduced amino acid sequences are highly homologous to those of other mammalian calsequestrins. As expected, the cardiac and skeletal calsequestrins are expressed specifically and exclusively in adult heart and skeletal muscles, respectively. In-situ hybridization was performed to examine the expression pattern of the calsequestrins in the developing mouse and rat embryos. During early organogenesis, the cardiac and skeletal calsequestrin transcripts were detected exclusively in the heart primordium and the myotome of somites, respectively. The cardiac calsequestrin transcripts were later detected in fetal heart and skeletal muscles, whereas the skeletal calsequestrin transcripts were only found in fetal skeletal muscles. These data suggest that the cardiac calsequestrin plays a role in the differentiation and function of heart, and in the function of fetal skeletal muscles in conjunction with the skeletal calsequestrin, but not in the early differentiation of the myotome of somites. The expression of the skeletal calsequestrin in the myotome is regulated probably by myogenin, a myogenic regulatory gene.

Localization of a 42-kDa inositol 1,3,4,5-tetrakisphosphate receptor protein in retina and change in expression after optic nerve injury

The mRNA and protein expression of a 42-kDa inositol 1,3,4,5-tetrakisphosphate receptor (InsP4R) was investigated in cryostat and paraffin sections from rat, porcine and bovine retina. InsP4R mRNA was localized by in situ hybridization in the ganglion cell layer, the inner nuclear cell layer and the outermost part of the outer nuclear cell layer. For immunocytochemistry, we used an antibody raised against a 19-amino-acid peptide (peptide-3) derived from previous microsequencing of proteolytic fragments of the porcine InsP4R (Stricker et al., FEBS Lett., 370 (1995) 236). The distribution of immunoreactivity was similar in all species investigated. Two cell types, most likely wide-field amacrine and retinal ganglion cells, were intensely stained. Prominent immunoreactivity in the on/off sublaminae of the inner plexiform layer and in the optic nerve layer indicates a pre- and/or post-synaptic localization of the protein. Moreover, significant InsP4R protein expression in the inner segment of photoreceptors points to a putative role of the second messenger InsP4 in signaling processes related to phototransduction. However, also the endfeet of Müller glia cells in the optic nerve layer were intensely stained. Optic nerve crush caused only minor changes in retinal InsP4R mRNA levels whereas InsP4R immunoreactivity was attenuated for more than 4 weeks in the photoreceptor inner segments, wide-field amacrine cells, and in retinal ganglion cells. The immunopositive sublaminae of the inner plexiform layer appeared to have shrunken. However, the signal intensity gradually recovered after 10 weeks. Since in parallel sections stained with a monoclonal antibody directed against the vesicular protein synaptophysin no changes were found, the alterations in InsP4R immunoreactivity induced by nerve injury are not due to a general decline in the expression of pre-synaptic proteins. We, therefore, hypothesize that the InsP4R might be linked to altered intracellular Ca2+ signaling after neuronal injury.

Induction of tetradecanoyl phorbol acetate-inducible sequence (TIS) genes by electroconvulsive shock in rat brain

We studied the induction of tetradecanoyl phorbol acetate-inducible sequences (TIS)1, 7, 8, 11, and 21 in rat cerebral cortex, hippocampus, and cerebellum after electroconvulsive shock (ECS). These genes were reported to be induced by depolarization in PC-12 cells. Single ECS induced TIS1, 8, 11, and 21, but not TIS7 genes in the rat brain regions examined. In cerebral cortex and hippocampus, induction of TIS1, TIS8, and TIS21 reached peak at 30 or 45 min after ECS. The induced mRNA of TIS1 and 21 decreased rapidly and returned almost to the basal level by 90 min after ECS, whereas those of TIS8 and 11 lasted longer. In cerebellum, TIS genes were induced and disappeared more rapidly than in the other two regions. The 10 and 20 daily ECSs did not affect the inducibility of TIS1, 11, and 21 in cerebellum, but the induction of TIS8 was attenuated by 35% after 20 daily ECSs. Our study indicated that ECS could induce some of the TIS genes in various rat brain regions, but the induction patterns were different depending on the TIS genes and brain regions. Our study also suggested that chronic ECS could not attenuate the induction of some immediate early genes.

Activation by ATP of a P2U 'nucleotide' receptor in an exocrine cell

1. We employed the perforated patch whole-cell technique to investigate the effects of ATP and other related nucleotides on membrane conductances in avian exocrine salt gland cells. 2. ATP (10 microM-1 mM) evoked an increase in maxi-K+ and Cl- conductances with a reversal potential of -35 mV. At lower concentrations of ATP (< or = 100 microM) responses were generally oscillatory with a sustained response observed at higher concentrations (> or = 200 microM). 3. Both oscillatory and sustained responses were abolished by the removal of bath Ca2+. In cells preincubated in extracellular saline containing reduced Ca2+, the application of ATP resulted in a transient increase in current. 4. As increasing concentrations of ATP (and related nucleotides) evoked a graded sequence of events with little run-down we were able to establish a rank order of potency in single cells. The order of potency of ATP analogues and agonists of the various P2-receptor subtypes was UTP > ATP = 2-methylthio-ATP > ADP. Adenosine (1 microM-1 mM), AMP (1 microM-1 mM), alpha,beta-methylene-ATP (1 microM-1 mM) and beta,gamma-methylene-ATP (1 microM-1 mM) were without effect. 5. In conclusion, although unable to preclude a role for a P2Y-receptor, our results suggest that ATP binds to a P2U-receptor increasing [Ca2+]i and subsequently activating Ca(2+)-sensitive K+ and Cl- currents.