bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of NGF and NT3 mRNAs in Hippocampal Interneurons Innervated by the GABAergic Septohippocampal Pathway
Authors: Rocamora Nativitat , Pascual Marta , Acsàdy Laszlo , de Lecea Luı́s , Freund Tamàs F. , Soriano Eduardo 
Published: April 2018

We usedin situhybridization for the detection of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin 3 (NT3) mRNAs combined with immunocytochemistry against the calcium-binding proteins parvalbumin (PARV), calbindin 28k (CALB), and calretinin (CALR) to determine the expression of neurotrophins in functionally distinct subsets of hippocampal interneurons. Most PARV-immunoreactive neurons in the hippocampus were NGF mRNA-positive (82%), which corresponds to 71% of NGF-positive neurons in the hippocampus proper and in the dentate gyrus (excluding granule cells). In contrast, only a subset of CALB- and CALR-immunoreactive interneurons (24% and 23%, respectively) displayed hybridization signals for NGF. Small subsets of PARV- and CALR-positive cells expressed NT3 mRNA, but we did not find hippocampal interneurons expressing BDNF mRNA. These results show that NGF and NT3 genes are differentially regulated in distinct subsets of GABAergic cells, and these interneurons are a major source of NGF production in the hippocampus.We also addressed whether hippocampal interneurons expressing neurotrophins were targets of the GABAergic septohippocampal pathway. We developed a triple-labeling method that combines anterograde tracing of this pathway by means ofPhaseolus vulgarisleucoagglutinin injections, within situhybridization for the detection of neurotrophins, and immunocytochemistry for calcium-binding proteins. Virtually every PARV-positive neuron innervated by GABAergic septohippocampal baskets expressed NGF mRNA (86%), whereas 39–59% of CALR- and CALB-positive interneurons that were contacted by GABAergic septohippocampal axons showed NGF gene expression. A small subset of NT3 mRNA-expressing interneurons was also innervated by septohippocampal baskets. These findings show that the GABAergic septohippocampal pathway preferentially terminates on interneurons expressing NGF mRNA, suggesting that this neurotrophic factor might be involved in the specification of this connection and in its maintenance and normal function in the adult brain.
Bidirectional Regulation of Protein Kinase Mζ in the Maintenance of Long-Term Potentiation and Long-Term Depression
Authors: Hrabetova Sabina , Sacktor Todd Charlton 
Published: April 2018

Long-term potentiation (LTP) and long-term depression (LTD) are persistent modifications of synaptic efficacy that may contribute to information storage in the CA1 region of the hippocampus. Persistently enhanced phosphorylation has been implicated in the maintenance phase of LTP. This hypothesis is supported by our previous observation that protein kinase Mζ (PKMζ), the constitutively active catalytic fragment of a single protein kinase C isoform (PKCζ), increases in LTP maintenance. In contrast, dephosphorylation may be important in LTD maintenance, because phosphatase inhibitors reverse established LTD, in addition to blocking its induction. Because phosphorylation is determined by a balance of phosphatases and kinases, both increases in phosphatase activity and decreases in kinase activity could contribute to LTD. We now report that the reduction of protein kinase activity by H7, as well as selective inhibition of PKC by chelerythrine, mimics and occludes the maintenance phase of homosynaptic LTD in rat hippocampal slices. Conversely, saturated LTD occludes the synaptic depression caused by chelerythrine. Biochemical analysis demonstrates a decrease of PKMζ, as well as PKCs γ and ε, in LTD maintenance and a concomitant loss of constitutive PKC activity. LTD and the downregulation of PKMζ are prevented by NMDA receptor antagonists and Ca2+-dependent protease inhibitors. Both LTD and the downregulation of PKMζ are reversible by high-frequency afferent stimulation. Our findings indicate that the molecular mechanisms of LTP and LTD maintenance are inversely related through the bidirectional regulation of PKC.
Ca2+-Permeable AMPA/Kainate and NMDA Channels: High Rate of Ca2+Influx Underlies Potent Induction of Injury
Authors: Lu You Ming , Yin Hong Zhen , Chiang Juna , Weiss John H. 
Published: April 2018

Neurodegeneration may occur secondary to glutamate-triggered Ca2+influx through any of three routes: NMDA channels, voltage-sensitive Ca2+channels (VSCC), and Ca2+-permeable AMPA/kainate channels (Ca-A/K). This study aims to examine Ca2+ion dynamics in the generation of excitotoxic injury by correlating the relative amounts of45Ca2+that flow into cortical neurons through each of these routes over a 10 min epoch (“10 min Ca2+loads;” a measure of influx rate), with resultant levels of intracellular free Ca2+([Ca2+]i) and subsequent injury. Neurons possessing Ca-A/K make up a small subset (∼13%) of cortical neurons in culture, which can be identified by a histochemical stain based on kainate-stimulated Co2+uptake (Co2+(+) neurons) and which are unusually vulnerable to AMPA/kainate receptor-mediated injury. Initial studies using brief kainate exposures (to selectively destroy Co2+(+) neurons) along with kainate-triggered45Ca2+influx measurements suggested that kainate causes rapid Ca2+influx into Co2+(+) neurons (comparable to that caused by NMDA). Influx through both Ca-A/K and NMDA channels increased proportionately with extracellular Ca2+, suggesting that these channels have high Ca2+permeability.When cultures were subjected to exposures that gave similar 10 min Ca2+loads through different routes, comparable levels of injury were observed, suggesting that net intracellular Ca2+accumulation is a critical determinant of injury. However, the relationship between [Ca2+]iand influx was less direct: although exposures that gave the lowest or highest 10 min Ca2+loads showed correspondingly lower or higher mean [Ca2+]iresponses, there appears to be a wide range of exposures over which individual neuronal differences and sequestration/buffering mechanisms obscure [Ca2+]ias a reflection of influx rate.
Rapid, Active Hair Bundle Movements in Hair Cells from the Bullfrog’s Sacculus
Authors: Benser Michael E. , Marquis Robert E. , Hudspeth A. J. 
Published: April 2018

Hair bundles, the mechanically sensitive organelles of hair cells in the auditory and vestibular systems, are elastic structures that are deflected by sound or acceleration. To examine rapid mechanical events associated with mechanoelectrical transduction, we stimulated individual hair bundles with flexible glass fibers and measured their responses with a temporal resolution of 400 μsec. When a hair bundle from the bullfrog’s sacculus was abruptly deflected in the positive direction, the bundle’s motion in the direction of stimulation was interrupted within the initial few milliseconds by an active movement, or twitch. This response was biphasic, with an initial component in the direction of the stimulus and a second component in the opposite direction. The amplitude and duration of the twitch depended on the bundle’s initial position and the size and rise time of the stimulus; the twitch was largest over the range of bundle deflections in which transduction was most sensitive. Under displacement clamp conditions, in which a hair bundle’s position was changed and then held constant with negative feedback, the twitch manifested itself as a biphasic force exerted by the bundle. Some hair bundles produced twitches in response to negatively directed stimuli, exhibited stimulus-evoked damped oscillations, or twitched spontaneously. The hair bundle’s ability to perform work against an external load and to oscillate in response to stimulation indicates that the bundle could supply feedback for mechanical amplification in vertebrate auditory organs.
Retinoic Acid Stimulates α-CAMKII Gene Expression in PC12 Cells at a Distinct Transcription Initiation Site
Authors: Chen Jing , Kelly Paul T. 
Published: April 2018

The promoter region of the α-subunit of the calcium/calmodulin-dependent protein kinase II (α-CaMKII) gene was inserted into a β-galactosidase (β-gal) reporter plasmid, and β-gal activities were examined in neuroblastoma (NB2a) and pheochromocytoma (PC12) cells after transient or stable transfections. The α-CaMKII promoter was 12- to 45-fold more active in NB2a compared with PC12 cells after transient or stable transfections. All-transretinoic acid (RA) stimulated reporter gene expression at both protein and mRNA levels in transfected PC12 cells. RA increased the level of endogenous α-CaMKII mRNA in untransfected PC12 cells by 4.4-fold. The transcription initiation site(s) (TIS) of the α-CaMKII gene in PC12 cells and rat brain was examined by RNase protection assays (RPA) and reverse transcriptase PCRs. The TIS for the α-CaMKII/β-gal reporter gene in transfected PC12 cells was indistinguishable from the TIS+1in rat hippocampus. In contrast, the only detectable TIS for the α-CaMKII gene in untransfected PC12 cells was located near the ATG translation start codon, 147 nucleotides 3′ to TIS+1in hippocampus. This unusual TIS was also the predominant TIS in rat cerebellum. These results suggest that the α-CaMKII promoter may contain sequences that respond directly or indirectly to RA. In addition, the unusual TIS of the α-CaMKII gene in PC12 cells and rat cerebellum may contribute to the very low expression of this gene compared with that in hippocampus.
Interkinetic and Migratory Behavior of a Cohort of Neocortical Neurons Arising in the Early Embryonic Murine Cerebral Wall
Authors: Takahashi Takao , Nowakowski Richard S. , Caviness Jr. Verne S. 
Published: April 2018

Neocortical neuronogenesis occurs in the pseudostratified ventricular epithelium (PVE) where nuclei of proliferative cells undergo interkinetic nuclear movement. A fraction of daughter cells exits the cell cycle as neurons (the quiescent, or Q, fraction), whereas a complementary fraction remains in the cell cycle (the proliferative, or P, fraction). By means of sequential thymidine and bromodeoxyuridine injections in mouse on embryonic day 14, we have monitored the proliferative and postmitotic migratory behaviors of 1 and 2 hr cohorts of PVE cells defined by the injection protocols. Soon after mitosis, the Q fraction partitions into a rapidly exiting (up to 50 μm/hr) subpopulation (Qr) and a more slowly exiting (6 μm/hr) subpopulation (Qs).QrandQsare separated as two distributions on exit from the ventricular zone with an interpeak distance of ∼40 μm. Cells inQrandQsmigrate through the intermediate zone with no significant change in the interpeak distance, suggesting that they migrate at approximately the same velocities. The rate of migration increases with ascent through the intermediate zone (average 2–6.4 μm/hr) slowing only transiently on entry into the developing cortex. Within the cortex,QrandQsmerge to form a single distribution most concentrated over layer V.
Activation of a Metabotropic Excitatory Amino Acid Receptor Potentiates Spike-Driven Calcium Increases in Neurons of the Dorsolateral Septum
Authors: Zheng Fang , Gallagher Joel P. , Connor John A. 
Published: April 2018

(1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD), an agonist for metabotropic glutamate receptors (mGluRs), causes depolarization and burst firing in rat dorsolateral septal nucleus (DLSN) neurons and results in long-term potentiation (LTP) at DLSN synapses. In the present study, we investigated whether these actions of 1S,3R-ACPD are attributable to the release of calcium from an inositol triphosphate-sensitive store after activation of mGluRs coupled to phospholipase C. Our data demonstrated that the ACPD-induced depolarization was associated with a small but significant decrease, not an increase, in [Ca2+]i; however, changes of [Ca2+]iduring ACPD-induced bursting were up to seven times larger than those produced by regular firing. Depletion of internal calcium stores by thapsigargin or ryanodine had a small to insignificant effect on the maximum changes of [Ca2+]iassociated with ACPD-induced bursting. Thus, elevation of [Ca2+]iduring firing by 1S,3R-ACPD is likely attributable to enhancement of calcium influx through voltage-gated channels and not to calcium release from internal stores. ACPD-induced burst firing elevated somatic and dendritic calcium levels up to 3 and 6 μm, respectively. Such an increase may be the underlying mechanism for ACPD-induced LTP as well as ACPD-induced acute cell death in rat DLSN.
Specific Induction of Protein Kinase Cδ Subspecies after Transient Middle Cerebral Artery Occlusion in the Rat Brain: Inhibition by MK-801
Authors: Miettinen Susanna , Roivainen Reina , Keinänen Riitta , Hökfelt Tomas , Koistinaho Jari 
Published: April 2018

Protein kinase C (PKC) consists of a family of closely related Ca2+/phospholipid-dependent phosphotransferase isozymes, most of which are present in the brain and are differentially activated by second messengers. Calcium-dependent PKC activity may cause neuronal degeneration after ischemic insult. PKC is also involved in trophic-factor signaling, indicating that activity of some PKC subspecies may be beneficial to the injured brain. Therefore, we screened long-term changes in the expression of multiple PKC subspecies after focal brain ischemia. Middle cerebral artery occlusion was produced by using an intraluminal suture for 30 min or 90 min. Inin situhybridization experiments, mRNA levels of PKCα, -β, -γ, -δ, -ε and -ζ were decreased in the infarct core 4 hr after ischemia and were lost completely 12 hr after ischemia. In areas surrounding the core, PKCδ mRNA was specifically induced 4, 12, and 24 hr after ischemia in the cortex. At 3 and 7 d, the core and a rim around it showed increased mRNA levels of PKCδ. No other subspecies were induced. At 2 d, immunoblotting demonstrated increased levels of PKCδ protein in the perifocal tissue, and immunocytochemistry revealed an increased number of PKCδ-positive neurons in the perifocal cortex. In the core, PKCδ-positive macrophages and endothelial cells were seen. Pretreatment with MK-801, an NMDA antagonist, inhibited cortical PKCδ mRNA induction. The data show that focal brain ischemia induces PKCδ mRNA and protein but not other PKC subspecies through the activation of NMDA receptors and that the upregulation lasts for several days in neurons of the perifocal zone.
δ Subunit Inhibits Neurosteroid Modulation of GABAAReceptors
Authors: Zhu Wei Jian , Wang Jian Feng , Krueger Karl E. , Vicini Stefano 
Published: April 2018

Neurosteroid modulation of GABAAreceptors has been observed with all subunit combinations investigated; however, hetero-oligomeric GABAAreceptors containing δ subunits were not studied previously. We describe the effect of δ subunit expression on 3α,21-dihydroxy-5α-pregnan-20-1 (THDOC)-induced potentiation of GABA-gated currents in transfected HEK 293 cells and in cerebellar granule cellsin vitro. THDOC (100 nm) significantly potentiated GABA-gated currents in cells transfected with combinations of α1, α6, β3, and γ2 subunit cDNAs, whereas cotransfection of δ subunit cDNA inhibited this potentiation. In contrast, the direct Cl−channel activation by THDOC at higher concentrations (1–10 μm) was not significantly dependent on δ subunit cotransfection. These results suggest that the presence of the δ subunit inhibits GABAAreceptor modulation but not the direct activation by neurosteroids. Cotransfection with δ subunit also affected the negative allosteric modulation by pregnenolone sulfate. THDOC potentiation of GABA-gated currents was greater in cerebellar granule cell cultures at 4 din vitro(DIV) compared with those at 14 DIV. Single-cell reverse transcription-PCR analysis of the mRNAs expressed in cultured cerebellar granule cells shows that an increased number of granule cells at 14 DIV express δ subunit mRNAs as compared with 4 DIV granule cells. The presence of δ subunit mRNAs detected in individual cells correlated well with the lack of sensitivity to THDOC. These results suggest that developmental expression of GABAAreceptor δ subunits may play an important role in determining the region-specific neurosteroid-induced modification of fast inhibitory synaptic function.
Modulation of Voltage-Gated Calcium Channels by Orphanin FQ in Freshly Dissociated Hippocampal Neurons
Authors: Knoflach Frederic , Reinscheid Rainer K. , Civelli Olivier , Kemp John A. 
Published: April 2018

Orphanin FQ (OFQ) has recently been reported to be an endogenous ligand for the opioid-like LC132 receptor. The effect of OFQ on high voltage-gated calcium channels (VGCCs) was examined in freshly dissociated rat pyramidal neurons using the whole-cell configuration of the patch-clamp technique. High-threshold Ba2+currents were reversibly inhibited by OFQ. The depression of the currents was associated with a slowed rate of activation and a change in the activationI–Vrelationship at step potentials higher than +30 mV. In concentration–response experiments, a mean (±SEM) pEC50value of 7.0 ± 0.07 and a Hill coefficient of 1.5 ± 0.08 (n = 5) were obtained. The near-maximum inhibition of the Ba2+currents by OFQ (1 μm) amounted to 31 ± 2.2% of control (n = 15). Opioid receptors could not account for the effects of OFQ on VGCCs, because naloxone, a broad spectrum μ-, δ-, and κ-receptor antagonist, did not reduce the effectiveness of OFQ. When GTP-γ-S was included in the pipette, the depression of the currents by OFQ was irreversible, whereas currents from neurons preincubated with pertussis toxin were not inhibited by OFQ, consistent with the involvement of a PTX-sensitive G-protein. When selective blockers of VGCCs were used, it was demonstrated that all subtypes of VGCCs were affected by OFQ. In conclusion, the effect of OFQ on VGCCs expressed in hippocampal CA3 and CA1 neurons may play an important role in the regulation of hippocampal cell excitability and neurotransmitter release.
Ryanodine-Sensitive Component of Calcium Transients Evoked by Nerve Firing at Presynaptic Nerve Terminals
Authors: Peng Yan-yi 
Published: April 2018

Whether Ca2+released from stores within the presynaptic nerve terminals also contributes to the Ca2+elevation evoked by action potentials was tested in intact bullfrog sympathetic ganglia. Intraterminal Ca2+transients (Δ[Ca2+]i) were evoked by electrical shocks to the presynaptic nerves at 20 Hz and were monitored by fura-2 fluorimetry. Ca2+released through intraterminal ryanodine-sensitive channels accounted for 46% of the peak Ca2+elevation. Moreover, in half of the terminals when intraterminal release was blocked by ryanodine, Δ[Ca2+]ireached a plateau at 200 ± 24 nm. Because 20 Hz is a frequency favorable for the release of a neuropeptide, luteinizing hormone releasing hormone (LHRH) from these presynaptic nerve terminals, and because the threshold level for LHRH release is 186 nm, intraterminal Ca2+release during nerve firing is likely to play a major role in regulating LHRH release. The intraterminal ryanodine channels were facilitated by caffeine as in other tissue. The releasable ryanodine-sensitive store could elevate the intraterminal [Ca2+] by an amount as high as 1.6 μmat a rate as fast as 250 nm/sec. The store could be refilled within 100 sec after a maximal discharge of its content by 20 Hz firing. Oscillation of [Ca2+]ievoked by 20 Hz nerve firing occurred in normal Ringer solution, in ryanodine, and in caffeine with a periodicity of ∼10 sec. Besides the facilitatory effects on the ryanodine-sensitive channels, caffeine also had inhibitory effects on Δ[Ca2+]ivia its action on a different process.
Amino Acid Signatures in the Primate Retina
Authors: Kalloniatis Michael , Marc Robert E. , Murry Ralph F. 
Published: April 2018

Pattern recognition of amino acid signals partitions virtually all of the macaque retina into 16 separable biochemical theme classes, some further divisible by additional criteria. The photoreceptor→bipolar cell→ganglion cell pathway is composed of six separable theme classes, each possessing a characteristic glutamate signature. Neuronal aspartate and glutamine levels are always positively correlated with glutamate signals, implying that they largely represent glutamate precursor pools. Amacrine cells may be parsed into four glycine-dominated (including one glycine/GABA immunoreactive population) and four GABA-dominated populations. Horizontal cells in central retina possess a distinctive GABA signature, although their GABA content is constitutively lower than that of amacrine cells and shows both regional and sample variability. Finally, a taurine–glutamine signature defines Müller’s cells. We thus have established the fundamental biochemical signatures of the primate retina along with multiple metabolic subtypes for each neurochemical class and demonstrated that virtually all neuronal space can be accounted for by cells bearing characteristic glutamate, GABA, or glycine signatures.
Ovarian Steroid Regulation of Tryptophan Hydroxylase mRNA Expression in Rhesus Macaques
Authors: Pecins-Thompson Melanie , Brown Nancy A. , Kohama Steven G. , Bethea Cynthia L. 
Published: April 2018

Progesterone (P) stimulates prolactin secretion through an unknown neural mechanism in estrogen (E)-primed female monkeys. Serotonin is a stimulatory neurotransmitter in prolactin regulation, and this laboratory has shown previously that E induces progestin receptors (PR) in serotonin neurons. Therefore, we questioned whether E and/or E+P increased serotonin neural function. The expression of mRNA for tryptophan hydroxylase (TPH) was examined in ovariectomized (spayed) control, E-treated (28 d), and E+P-treated monkeys (14 d E and 14 d E+P) usingin situhybridization and a 249 bp TPH cRNA probe generated with RT-PCR (n = 5 animals/group). Densitometric analysis of film autoradiographs revealed a ninefold increase in TPH mRNA in E-treated macaques compared to spayed animals (p < 0.05). With supplemental P treatment, TPH mRNA signal was increased fivefold over spayed animals (p < 0.05), but was not significantly different compared to E-treated animals. These results were verified by grain counts from photographic emulsion-coated slides. There were significantly higher single-cell levels of TPH mRNA in serotonergic neurons of the dorsal raphe in E- and E+P-treated groups (p < 0.05). These data indicate that E induces TPH gene expression in nonhuman primates and that the addition of P has little additive effect on TPH gene expression. Thus, the action of P on prolactin secretion is probably not mediated at the level of TPH gene transcription. However, because P increases raphe serotonin content in E-primed rodents, the possibility remains that P may have other actions on post-translational processing or enzyme activity.