bluuebunny/crossref_metadata_2025 huggingface dataset:
NGF gene expression in actively growing brain glia
Authors: Lu B , Yokoyama M , Dreyfus CF , Black IB
Published: March 2018

Previous work suggested that brain NGF acts locally on cells adjacent to sites of synthesis, in addition to any putative actions on distant, projecting perikarya. To define the basis of local action, we used a sensitive nuclease protection assay to identify cells expressing the NGF gene in vivo and in vitro. In addition to neurons, glia from a variety of developing brain areas synthesized NGF mRNA, suggesting that CNS glia exhibit a generalized capacity to express the gene. Expression was associated with active glial growth. Stimulation of growth with serum increased NGF message 2-fold in culture. Moreover, rapidly growing, low-density glial cultures exhibited 8-fold higher levels of NGF mRNA than quiescent, confluent cultures. The optic nerve, which contains all 3 major types of glia, expressed the message in vivo during neonatal development. In contrast, expression was barely detectable in the adult optic nerve. Transection, which induces glial proliferation, elicited de novo appearance of NGF mRNA in the adult nerve. Our observations suggest that active glial growth is associated with expression of the NGF gene and raise the possibility that actively growing glia in the developing or injured brain regulate neuronal growth through the elaboration of NGF.
A growth factor from neuronal cell lines stimulates myelin protein synthesis in mammalian brain
Authors: Giulian D , Johnson B , Krebs JF , Tapscott MJ , Honda S
Published: March 2018

Oligodendroglia growth factor (OGF) is a 16-kDa soluble protein produced by neuronal cell lines. This factor, when incubated with brain glia in culture, selectively stimulates growth of oligodendroglia, the myelin-producing cells of the CNS. OGF infused into the cerebral cortex of the adult rat accelerates the production of myelin proteins as shown by increased specific activity of the myelin enzyme 2′,3′-cyclic nucleotide 3′-phosphohydrolase (2′,3′-CNPase), by stimulated synthesis of myelin basic protein, and by elevations in levels of myelin proteolipid protein RNA. The ability of OGF to induce myelin protein production in vivo suggests that neuron-secreted growth factors help to regulate myelin formation within the CNS.
Estrogen-enhanced neurite growth: evidence for a selective induction of Tau and stable microtubules
Authors: Ferreira A , Caceres A
Published: March 2018

Estrogen stimulates the neurite outgrowth response of medial basal hypothalamic neurons maintained in culture. We show here that one effect of estrogen is to promote an increase in tau, but not in tubulin, microtubule-associated protein 1a (MAP-1a), or MAP-2 protein levels. This response precedes and accompanies an increase in stable microtubules and in neurite length. Taken collectively, our data suggest that estrogen-enhanced neurite growth is mediated by a selective induction of microtubule-stabilizing factors, namely, the tau proteins.
Voltage-gated currents in identified rat olfactory receptor neurons
Authors: Trombley PQ , Westbrook GL
Published: March 2018

Whole-cell recording techniques were used to characterize voltage-gated membrane currents in neonatal rat olfactory receptor neurons (ORNs) in cell culture. Mature ORNs were identified in culture by their characteristic bipolar morphology, by retrograde labeling techniques, and by olfactory marker protein (OMP) immunoreactivity. ORNs did not have spontaneous activity, but fired action potentials to depolarizing current pulses. Action potentials were blocked by tetrodotoxin (TTX), which contrasts with the TTX-resistant action potentials in salamander olfactory receptor cells (e.g., Firestein and Werblin, 1987). Prolonged, suprathreshold current pulses evoked only a single action potential; however, repetitive firing up to 35 Hz could be elicited by a series of brief depolarizing pulses. Under voltage clamp, the TTX- sensitive sodium current had activation and inactivation properties similar to other excitable cells. In TTX and 20 mM barium, sustained inward current were evoked by voltage steps positive to -30 mV. This current was blocked by Cd (100 microM) and by nifedipine (IC50 = 368 nM) consistent with L-type calcium channels in other neurons. No T-type calcium current was observed. Voltage steps positive to -20 mV also evoked an outward current that did not inactivate during 100-msec depolarizations. Tail current analysis of this current was consistent with a selective potassium conductance. The outward current was blocked by external tetraethylammonium but was unaffected by Cd or 4- aminopyridine (4-AP) or by removal of external calcium. A transient outward current was not observed. The 3 voltage-dependent conductances in cultured rat ORNs appear to be sufficient for 2 essential functions: action potential generation and transmitter release. As a single odorant-activated channel can trigger an action potential (e.g., Lynch and Barry, 1989), the repetitive firing seen with brief depolarizing pulses suggests that ORNs do not integrate sensory input, but rather act as high-fidelity relays such that each opening of an odorant- activated channel reaches the olfactory bulb glomeruli as an action potential.
Principal neurons and small intensely fluorescent (SIF) cells in the rat superior cervical ganglion have distinct developmental histories
Authors: Hall AK , Landis SC
Published: March 2018

Sympathetic ganglia contain 2 adrenergic derivatives of the neural crest: principal neurons and small, intensely fluorescent (SIF) cells. The developmental mechanisms responsible for the generation of these 2 cell classes in vivo are not well understood. To examine the possible developmental and lineage relationships between differentiating principal neurons and SIF cells, a fluorescence microscopic study utilizing antibodies against tyrosine hydroxylase (TH) and catecholamine histofluorescence has been combined with the ultrastructural examination of embryonic and postnatal rat superior cervical ganglia (SCG). On embryonic day 12.5, before neuroblasts had become postmitotic, the cells in the SCG possessed intense TH immunoreactivity and had weak to bright catecholamine histofluorescence, but no cells displayed the fine structure of mature SIF cells or neurons. At embryonic days 16.5 and 18.5, postmitotic principal neurons expressed more moderate levels of TH and catecholamines characteristic of the late embryonic and postnatal SCG. By contrast, a small number of cells containing intense TH or catecholamine fluorescence were present in embryonic day 16.5 and older ganglia. Almost all of the intensely fluorescent cells observed were found apposed to capillaries within the ganglion. These embryonic intensely fluorescent cells were larger than SIF cells seen postnatally. Ultrastructural examination of developing ganglia confirmed that cells containing numerous large, dense-cored vesicles (LDCVs) were a prominent feature of ganglia that also contained intensely fluorescent cells. In addition, some embryonic cells containing LDCVs were mitotic. From these and other studies, it seems likely that during development, neuron precursors, in response to differentiation factors such as fibroblast growth factor (FGF) and/or NGF, acquire overt neuronal traits and become postmitotic. Subsequently, cells resembling mature SIF cells appear next to blood vessels, where they may have received other instructional signals such as glucocorticoids. This developmental scheme suggests that the differentiation of principal neurons and SIF cells is independently regulated, and that the ability of SIF cells to convert into principal neurons observed in vitro cannot account for the generation of neurons in vivo.
Stages of growth of hamster retinofugal axons: implications for developing axonal pathways with multiple targets
Authors: Bhide PG , Frost DO
Published: March 2018

Neurons in many regions of the CNS (e.g., cortical areas, thalamic nuclei) are heterogeneous with regard to their afferent and efferent connections. Using the hamster retinofugal system as a model, we investigated the mechanisms by which such connectional heterogeneity arises during ontogeny. Retinal ganglion cell axons were labeled with 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (Dil) in paraformaldehyde-fixed tissue. The fluorescent label was photoconverted to a diaminobenzidine reaction product. The morphology of the axons, including their trajectories, branching patterns, and growth cones, was studied at the level of the dorsal lateral geniculate nucleus (LGd) from embryonic day 14 to adulthood. In adult hamsters, axons of retinal ganglion cells (RGCs) are spatially segregated at the level of the lateral geniculate nucleus into a superficial optic tract, situated just beneath the pia, and an internal optic tract consisting of fascicles running parallel to the pia within the geniculate. All retinofugal axons project to the midbrain, but only superficial optic tract axons emit collaterals to the LGd. During development, axons in both divisions of the optic tract emit collaterals to the LGd, but by postnatal day 15, collaterals of internal optic tract axons are virtually entirely eliminated, whereas those of superficial optic tract axons have elaborated terminal arbors. Thus, the heterogeneity among different classes of RGCs with respect to their efferent connections emerges by the selective stabilization, by each class, of a unique subset of connections from an initially widespread set shared by all classes. Thalamic collaterals of RGC axons emerge along established axon trunks, not by bifurcation of the growing tip. This occurs after the axons have grown past the thalamus and, presumably, entered their targets in the midbrain. Growth cones at the tips of elongating axon trunks are larger in size and have a more “complex” morphology compared to the growth cones on collaterals. Axons of RGCs develop in 3 morphologically distinct growth states. First, they elongate to their most distant targets in the midbrain. Then, they simultaneously emit unbranched or poorly branched collaterals to multiple targets. Finally, they elaborate terminal arbors in their definitive targets and eliminate their other collaterals. This developmental strategy may be paradigmatic for the formation of long CNS pathways with multiple targets. Furthermore, these data document, at the single-axon level, the steps in the elaboration and withdrawal of transient neuronal projections.
Synapsin I and Synaptophysin expression during ontogenesis of the mouse peripheral vestibular system
Authors: Scarfone E , Dememes D , Sans A
Published: March 2018

Synapsin I and Synaptophysin are selectively localized in axonal endings of CNS neurons where they are associated with small synaptic vesicle membranes. The development of expression of these 2 proteins was studied by immunocytochemistry during ontogenesis of the peripheral vestibular system in the mouse. Both proteins are localized in vestibular ganglion neurons and in their peripheral sensory extensions as early as gestational day 14. While the entire periphery of these fibers is labeled during embryogenesis, both proteins are subject to relocation during the postnatal maturation of these fibers. In the mature vestibular receptors they disappear from the fibers themselves but are found concentrated in their intraepithelial endings and in the neuronal cell body. These observations show that the distribution pattern of Synapsin I and Synaptophysin in peripheral extensions of vestibular afferent neurons during development is identical to that described in axonal processes of CNS neurons. This suggests that the peripheral processes of the vestibular afferent neurons present structural and biochemical characteristics of axons. These characteristics are consistent with a bimodal sensory and secretory function of mature endings.
Primary culture of neonatal rat olfactory neurons
Authors: Ronnett GV , Hester LD , Snyder SH
Published: March 2018

We have prepared primary cultures of purified neonatal rat olfactory neurons. Dissociated olfactory epithelial cells are maintained in modified Eagle's medium with D-valine, cytosine arabinoside, and NGF. NGF is required for neuronal survival. Immunohistochemical staining is positive for the neuronal markers vimentin, olfactory marker protein, and neuron-specific enolase, but negative for the glial markers, glial fibrillary acidic protein, and S-100 protein. Physiologic concentrations of odorants stimulate cAMP accumulation in the cells. Because of their morphology, biochemical composition, and responsiveness to odorants, these cells should enhance olfactory investigations.
Distinct presynaptic regulation of dopamine release through NMDA receptors in striosome- and matrix-enriched areas of the rat striatum
Authors: Krebs MO , Trovero F , Desban M , Gauchy C , Glowinski J , Kemel ML
Published: March 2018

Striosome- and matrix-enriched striatal zones were defined in coronal and sagittal brain sections of the rat, on the basis of 3H-naloxone binding to mu-opiate receptors (a striosome-specific marker). Then, using a new in vitro microsuperfusion device, the NMDA (50 microM)- evoked release of newly synthesized 3H-dopamine (3H-DA) was examined in these four striatal areas under Mg(2+)-free conditions. The amplitudes of the responses were different in striosomal (171 +/- 6% and 161 +/- 5% of the spontaneous release) than in matrix areas (223 +/- 6% and 248 +/- 12%), even when glycine (1 or 100 microM) was coapplied (in the presence of 1 microM strychnine). In the four areas, the NMDA-evoked release of 3H-DA was blocked completely by Mg2+ (1 mM) or (+)-5-methyl- 10,11-dihydro-5H-dibenzo(a,d)cyclohepten-5,10-imine maleate (MK-801; 1 microM) and almost totally abolished by kynurenate (100 microM). Because the tetrodotoxin (TTX)-resistant NMDA-evoked release of 3H-DA was similar in striosome- (148 +/- 5% and 152 +/- 6%) or matrix- enriched (161 +/- 5% and 156 +/- 7%) areas, the indirect (TTX- sensitive) component of NMDA-evoked responses, which involves striatal neurons and/or afferent fibers, seems more important in the matrix- than in the striosome-enriched areas. The modulation of DA release by cortical glutamate and/or aspartate-containing inputs through NMDA receptors in the matrix appears thus to be partly distinct from that observed in the striosomes, providing some functional basis for the histochemical striatal heterogeneity.
Glutamate receptor subtypes mediate excitatory synaptic currents of dopamine neurons in midbrain slices
Authors: Mereu G , Costa E , Armstrong DM , Vicini S
Published: March 2018

Although dopamine (DA)-containing neurons participate in a number of important cerebral functions, the physiology of their synaptic connections is poorly understood. By using whole-cell patch-clamp recording in thin slices of rat mesencephalon, we have investigated the biophysical properties of synaptic events and the nature of neurotransmitter(s) and receptors involved in the synaptic input to DA neurons in substantia nigra. The histological and electrophysiological characteristics of these cells were consistent with those described by recent in vivo and in vitro studies, thus allowing their unequivocal identification. Under appropriate experimental conditions, intranigral stimulation produced excitatory synaptic inputs in DA neurons. By voltage-clamp analysis, most of these excitatory postsynaptic currents (EPSCs) had a rise time of about 1.0 msec and a decay phase that could be fit by the sum of two exponential curves so that a fast and a slow component could be distinguished. The slow component was enhanced by glycine, by removing Mg2+ from the bath medium, or by membrane depolarization. Moreover, the slow component was consistently decreased by selective antagonists of NMDA receptors, whereas an antagonist for the non-NMDA receptors abolished the fast component slightly affecting the slow component and reduced peak EPSC amplitude. The results indicate that both NMDA-sensitive and non-NMDA-sensitive glutamate receptors contribute to EPSCs of DA neurons. Therefore, it is suggested that these receptors may play a critical role in the physiology (control of excitability, pacemaker firing, and dendritic DA release) as well as pathology (neuronal death in Parkinson's disease, psychosis, and mechanism of action of drugs of abuse, such as ethanol) related to DA neurons.
Halothane blocks low-voltage-activated calcium current in rat sensory neurons
Authors: Takenoshita M , Steinbach JH
Published: March 2018

Although volatile anesthetic agents have been used clinically for many years, the mechanisms by which they act on the nervous system to produce anesthesia are not known. A possible site of action is the voltage-gated calcium-selective channel (Krnjevic and Puil, 1988). Accordingly, the action of the halogenated alkane anesthetic halothane on voltage-dependent Ca currents in neonatal rat sensory neurons was examined using whole-cell patch-clamp recordings. Halothane reversibly reduced the low-voltage-activated Ca current with an EC50 of about 100 microM. Similar effects were seen using a halogenated ether anesthetic (isoflurane) and in sensory neurons from adult rats. At higher concentrations, both halothane and isoflurane reduced the high-voltage- activated Ca current. Because low-voltage-activated Ca current. Because low-voltage-activated Ca current has been postulated to be involved in the control of neuronal excitability and bursting (Llinas, 1988), this block may explain some of the clinical actions of volatile anesthetics.
Prior exposure to chronic stress results in enhanced synthesis and release of hippocampal norepinephrine in response to a novel stressor
Authors: Nisenbaum LK , Zigmond MJ , Sved AF , Abercrombie ED
Published: March 2018

The release and synthesis of norepinephrine (NE) in hippocampus were measured in naive and chronically cold-stressed rats in response to acute tail-shock stress. Using in vivo microdialysis, it was determined that the basal extracellular concentrations of NE and 3,4- dihydroxyphenylacetic acid (DOPAC) in hippocampus were the same in the two groups. However, 30 min of intermittent tail shock produced a greater elevation of extracellular NE and 3,4-dihydroxyphenylacetic acid in the chronically cold-stressed rats than in the native controls. In hippocampus, the extracellular concentration of DOPAC may reflect NE biosynthesis, and thus the enhanced DOPAC response in the chronically stressed rats suggests an increase in NE synthesis. In order to investigate this possibility, two further methods of assessing NE biosynthesis were employed. Tyrosine hydroxylase (TH) activity was assayed in vitro in the presence of saturating concentrations of cofactor. No change in maximal TH activity could be detected in hippocampus of chronically cold-stressed rats. In addition, the in vivo rate of tyrosine hydroxylation in cold-stressed rats was measured by the accumulation of 3,4-dihydroxyphenylalanine in tissue following inhibition of aromatic amino acid decarboxylase. It was found that, whereas basal synthesis was the same in both groups of rats, synthesis accompanying a novel stressor was increased to a greater extent in the chronically stressed rats.
The distribution of synapsin I and synaptophysin in hippocampal neurons developing in culture
Authors: Fletcher TL , Cameron P , De Camilli P , Banker G
Published: March 2018

As a first step toward elucidating mechanisms involved in the sorting of synaptic vesicle proteins in neurons, we have used immunofluorescence microscopy to determine the distribution of two synaptic vesicle proteins, synapsin I and synaptophysin, in hippocampal neurons developing in culture. In mature cultures, synapsin I and synaptophysin immunoreactivity was concentrated in puncta that were restricted to sites where axons contacted neuronal cell bodies or dendrites. Electron-microscopic immunocytochemistry demonstrated that these puncta corresponded to vesicle-filled axonal varicosities that were exclusively presynaptic. At early stages of development, before cell-cell contact, both synapsin I and synaptophysin were preferentially localized in axons, where they were particularly concentrated in the distal axon and growth cone. In axons that did not contact other cells, immunostaining for these two proteins had a granular appearance, which persisted for at least 7 d, but focal accumulations of vesicles comparable to those seen at sites of synaptic contact were not observed. When neurons contacted one another, numerous puncta of synapsin I and synaptophysin formed within the first week in culture. Double-label immunofluorescence demonstrated that the two vesicle antigens were closely codistributed throughout these stages of development. These observations demonstrate that synaptic vesicle proteins assume a polarized distribution within nerve cells beginning early in development, as soon as the axon can be identified. In contrast, differences in microtubule polarity orientation that distinguish mature axons and dendrites, and that have been proposed to account for the selective sorting of some materials in nerve cells, first appear at a subsequent stage of development. The selective distribution of synaptic vesicle proteins to the axon occurs in isolated cells, independent of interactions with other cells. In contrast, the formation of large clusters of vesicles typical of presynaptic specializations requires contact with an appropriate postsynaptic target. Thus, in cultured hippocampal neurons, the localization of synaptic vesicles in presynaptic specializations is the result of sorting mechanisms intrinsic to individual neurons as well as to mechanisms mediated by cell-cell contact.
Acetylcholine receptor expression in developing chick ciliary ganglion neurons
Authors: Jacob MH
Published: March 2018

Little is known about the levels of nicotinic ACh receptors (AChRs) in neurons prior to innervation and whether the distribution and number of receptors change in response to innervation. In the present study, AChR levels were examined in developing chick ciliary ganglion neurons in situ at stages preceding and during early and late phases of synaptogenesis. AChRs were localized in surface and intracellular pools of intact and saponin-permeabilized ganglionic neurons, respectively, by using a highly sensitive immunocytochemical approach that included the binding of an anti-AChR monoclonal antibody (mAb) followed by a biotinylated secondary antibody and an avidin-biotinylated HRP complex. At older stages of development, embryonic day (ED) 7–7.5 and ED 11, when all of the neurons are known to be receiving synaptic contacts, AChRs were present in both internal and surface pools. Within the neurons, AChRs were associated with organelles that function in the biosynthesis, processing, and transport of integral plasma membrane proteins. On the surface of the neurons, AChRs were predominantly localized in the specialized postsynaptic membrane, with low levels of AChRs being present in extrasynaptic regions. The earliest stage at which synapses could be detected in the ganglion was ED 4.5. Synapses were detected by light microscopic immunocytochemical labeling with anti-SV2, an mAb to a synaptic vesicle protein, and by ultrastructural analysis. At this stage, most of the neurons were not labeled by the anti-AChR mAb, while a few neurons had dense deposits of reaction product on the rough endoplasmic reticulum and portions of the nuclear envelope. Low levels of reaction product were also found on the surface of a small number of neurons, being localized predominantly on the specialized postsynaptic membrane of the few immature synapses present. Occasionally, small patches of labeling were observed in extrasynaptic regions. In contrast, little internal and no surface anti-AChR immunolabeling was detected in ciliary ganglion neurons prior to innervation, at ED 3.5–4. The finding of a large increase in both internal and surface AChR levels in the neurons at the time of innervation suggests that signals from the presynaptic input play an important role in the induction of AChR expression in neurons.
Temperature-dependent peptidergic feedback: potential role in seasonal egg laying in Aplysia
Authors: Redman RS , Berry RW
Published: March 2018

alpha-Bag cell peptide (alpha-BCP), one of the secretory products of the neuroendocrine bag cells in Aplysia, has been reported by various investigators to have either excitatory or inhibitory feedback effects. Though conflicting, these results may be explained by the difference in temperature at which the experiments were performed. Because egg laying in this animal is temperature dependent, the alteration in function of this peptide by temperature may offer a possible molecular basis for the seasonal regulation of egg laying. This hypothesis was investigated by assessing the feedback actions of alpha-BCP at various temperatures. At 15 degrees C, alpha-BCP hyperpolarized bag cells, shortened the duration of synaptically evoked bag cell discharges, and reduced the number of action potentials per discharge. However, at 20 degrees C, the peptide depolarized bag cells, lengthened discharges, and increased the number of action potentials per discharge. A temperature-dependent influence on bag cell cAMP levels may underlie these effects, because alpha-BCP reduced basal cAMP levels in intact bag cells at temperatures of 15 degrees C and below, while at 17–22 degrees C it increased these levels. However, the inhibitory effects of alpha-BCP on stimulated adenylate cyclase activity in bag cell homogenates were not temperature dependent. Moreover, a low-Ca2+/high-Mg2+ solution abolished alpha- BCP's ability to increase bag cell cAMP levels at 20 degrees C. This suggests that the peptide may evoke the secretion of an excitatory modulator at the higher temperature. These results imply that alpha-BCP is autoinhibitory at typical winter temperatures, but becomes autoexcitatory as ocean temperature rises in the summer. Thus, the peptide may function in coordination with other factors to regulate egg laying in response to seasonal temperature variations.
Modulation of calcium channels in human retinal glial cells by basic fibroblast growth factor: a possible role in retinal pathobiology
Authors: Puro DG , Mano T
Published: March 2018

The objective of this study was to begin to examine the cellular and biophysical effects on human retinal glial cells of basic fibroblast growth factor (bFGF), which is endogenous to the retina and likely to play a role in retinal pathobiology. Experiments were performed on cultured glial cells derived from the adult postmortem retina. A proliferative response to bFGF established a sensitivity of the retinal glia to this growth factor. The possibility that bFGF alters calcium currents was assessed using the whole-cell recording configuration of the patch-clamp technique to analyze inward currents carried by barium. Two types of voltage-gated calcium channels could be expressed by the glial cells. One, similar to the T-type current described in various kinds of cells, had a low threshold of activation, a transient response, and an insensitivity to the dihydropyridine nifedipine. The other type of inward current, which closely resembles the L-type calcium current found in other cells, had a high threshold, had a long- lasting response, and was inhibited by nifedipine. When continuous whole-cell recordings were made from retinal glial cells, the L-type calcium current increased significantly within 20 min after exposure of the cells to bFGF. The physiological significance of this modulatory effect remains uncertain, though the observation that nifedipine inhibits both the L-type calcium current and the bFGF-induced proliferation is consistent with the hypothesis that dihydropyridine- sensitive channels may play a role in modulating the mitogenic response of retinal glial cells to this growth factor.
The effect of amphetamine on regional cerebral blood flow during cognitive activation in schizophrenia
Authors: Daniel DG , Weinberger DR , Jones DW , Zigun JR , Coppola R , Handel S , Bigelow LB , Goldberg TE , Berman KF , Kleinman JE
Published: March 2018

To explore the role of monoamines on cerebral function during specific prefrontal cognitive activation, we conducted a double-blind placebo- controlled crossover study of the effects of 0.25 mg/kg oral dextroamphetamine on regional cerebral blood flow (rCBF) as determined by 133Xe dynamic single-photon emission-computed tomography (SPECT) during performance of the Wisconsin Card Sorting Test (WCST) and a sensorimotor control task. Ten patients with chronic schizophrenia who had been stabilized for at least 6 weeks on 0.4 mg/kg haloperidol participated. Amphetamine produced a modest, nonsignificant, task- independent, global reduction in rCBF. However, the effect of amphetamine on task-dependent activation of rCBF (i.e., WCST minus control task) was striking. Whereas on placebo no significant activation of rCBF was seen during the WCST compared with the control task, on amphetamine significant activation of the left dorsolateral prefrontal cortex (DLPFC) occurred (p = 0.0006). Both the mean number of correct responses and the mean conceptual level increased (p less than 0.05) with amphetamine relative to placebo. In addition, with amphetamine, but not with placebo, a significant correlation (p = - 0.71; p less than 0.05) emerged between activation of DLPFC rCBF and performance of the WCST task. These findings are consistent with animal models in which mesocortical catecholaminergic activity modulates and enhances the signal-to-noise ratio of evoked cortical activity.
Actin dynamics in growth cones
Authors: Okabe S , Hirokawa N
Published: March 2018

The mechanism of actin incorporation and turnover in the nerve growth cone was examined by immunoelectron microscopy and low-light-level video microscopy of cultured neurons injected with biotin-labeled actin or fluorescently labeled actin. We first determined the sites of actin incorporation into the cytoskeleton of growth cones by immunoelectron microscopy of cultured neurons injected with biotin-labeled actin and reacted with an anti-biotin antibody and a gold-labeled secondary antibody. Shortly after the injection, biotin-actin molecules incorporated into the cytoskeleton were localized in the distal part of actin bundles in the filopodia and at the membrane-associated fringe of the actin filament network. With longer incubation, most actin polymers in the growth cones were labeled uniformly, suggesting that actin subunits are added preferentially at the membrane-associated ends of preexisting actin filaments. We then determined whether actin filaments translocate within the growth cones by low-light-level video microscopy of living neurons injected with fluorescently labeled actin and photobleached with a laser beam. When actin fluorescence at the leading edge of a growth cone was bleached, a rearward translocation of the bleached spot toward the base of the growth cone was observed. This observation suggests the presence of a rearward flow of actin polymers within growth cones. Taken together, these results indicate that there is a continuous addition of actin monomers at the leading edge of the growth cone and a successive rearward translocation of the assembled filaments.
Neuronal expression of nuclear and mitochondrial genes for cytochrome oxidase (CO) subunits analyzed by in situ hybridization: comparison with CO activity and protein
Authors: Hevner RF , Wong-Riley MT
Published: March 2018

Cytochrome oxidase (CO) is a mitochondrial energy-generating enzyme of the oxidative phosphorylation pathway. In neurons, CO activity varies among different cells and compartments (perikarya, dendrites, axons, and terminals) according to their physiological activity and metabolic requirements. Regulation of enzyme protein levels, rather than enzyme turnover number, largely accounts for local variations in CO activity (Hevner and Wong-Riley, 1989, 1990). In the present study, we examined how CO activity and protein levels are related to mitochondrial DNA (mtDNA) and CO subunit mRNA levels in neurons and neuronal compartments. Mammalian CO comprises 13 subunits (Kadenbach et al., 1983), of which three are encoded in mtDNA and 10 in nuclear genes. We studied one mitochondrial-encoded mRNA [subunit I (COI)], two nuclear- encoded mRNAs (COIV, COVIII), and mtDNA, using in situ hybridization to determine their distributions in monkey hippocampus, cerebellum, and primary visual cortex. We compared their distributions with those of CO activity and protein, determined by histochemistry and immunohistochemistry, respectively. In all regions, the local content of mtDNA was similar, but not identical, to the activity and amount of CO. Expression of COI mRNA was not proportional to mtDNA abundance or CO activity and protein, but instead was highest in cell bodies, lower in dendrites, and undetectable in axon terminals. COIV and COVIII mRNAs were detected exclusively in perikarya and proximal dendrites. Thus, the nuclear-encoded subunits of CO are probably translated mainly in neuronal cell bodies and allocated to other compartments posttranslationally. Regulation of CO was studied in two monkeys treated by monocular tetrodotoxin (TTX) injection, a procedure that blocks impulses from one eye. In those animals, cortical changes in CO activity were correlated with changes in mtDNA and in COI, COIV, and COVIII mRNA. Our results suggest that neuronal CO is synthesized and assembled mainly in cell bodies and indicate that both nuclear and mitochondrial CO subunit genes are regulated by neuronal activity.
A detailed model of the primary visual pathway in the cat: comparison of afferent excitatory and intracortical inhibitory connection schemes for orientation selectivity
Authors: Worgotter F , Koch C
Published: March 2018

In order to arrive at a quantitative understanding of the dynamics of cortical neuronal networks, we simulated a detailed model of the primary visual pathway of the adult cat. This computer model comprises a 5 degrees x 5 degrees patch of the visual field at a retinal eccentricity of 4.5 degrees and includes 2048 ON- and OFF-center retinal beta-ganglion cells, 8192 geniculate X-cells, and 4096 simple cells in layer IV in area 17. The neurons are implemented as improved integrate-and-fire units. Cortical receptive fields are determined by the pattern of afferent convergence and by inhibitory intracortical connections. Orientation columns are implemented continuously with a realistic receptive field scatter and jitter in the preferred orientations. We first show that realistic ON-OFF-responses, orientation selectivity, velocity low-pass behaviour, null response, and responses to spot stimuli can be obtained with an appropriate alignment of geniculate neurons converging onto the cortical simple cell (Hubel and Wiesel, 1962) and in the absence of intracortical connections. However, the average receptive field elongation (length to width) required to obtain realistic orientation tuning is 4.0, much higher than the average observed elongation. This strongly argues for additional intracortical mechanisms sharpening orientation selectivity. In the second stage, we simulated five different inhibitory intracortical connection patterns (random, local, sparse-local, circular, and cross-orientation) in order to investigate the connection specificity necessary to achieve orientation tuning. Inhibitory connection schemes were superimposed onto Hubel and Wiesel-type receptive fields with an elongation of 1.78. Cross-orientation inhibition gave rise to different horizontal and vertical orientation tuning curves, something not observed experimentally. A combination of two inhibitory schemes, local and circular inhibition (a weak form of cross-orientation inhibition), is in good agreement with observed receptive field properties. The specificity required to establish these connections during development is low. We propose that orientation selectivity is caused by at least three different mechanisms (“eclectic” model): a weak afferent geniculate bias, broadly tuned cross-orientation inhibition, and some iso-orientation inhibition. The most surprising finding is that an isotropic connection scheme, circular inhibition, in which a cell inhibits all of its postsynaptic target cells at a distance of approximately 500 microns, enhances orientation tuning and leads to a significant directional bias. This is caused by the embedding of cortical cells within a columnar structure and does not depend on our specific assumptions.
The regulation of transmitter expression in postembryonic lineages in the moth Manduca sexta. I. Transmitter identification and developmental acquisition of expression
Authors: Witten JL , Truman JW
Published: March 2018

The majority of the neurons in the adult nervous system of Manduca sexta are born postembryonically, during larval life. Stereotypic arrays of identifiable neuroblasts generate their clonal families or lineages commencing at the end of the second larval instar through pupal day 2, when the neuroblasts die (Booker and Truman, 1987a). We have used immunohistochemical techniques to follow the neurochemical differentiation of GABA and a peptide similar to molluscan small cardioactive peptide B (SCPB) in identified lineages. We report here the distribution and developmental acquisition of the expression of these putative transmitters. There are 24 postembryonic lineages in the second thoracic ganglion of the larvae (Booker and Truman, 1987a). Immunoreactivity against GABA and SCPB is seen only in a subset of these 24 clonal families. GABA immunoreactivity is confined to the progeny of the E, K, M, N, T, and X neuroblasts and is expressed by most or all of the neurons in these lineages. The SCPB-like immunoreactivity is found in a subset of the neurons in only two clonal groups, the K and M groups, and is colocalized with GABA. These results show that, though heterogeneity in transmitter type exists (GABA, GABA/SCPB), members of a given lineage share at least some features (GABA) in common. The onset of transmitter expression was followed in detail for the K- and M-lineage neurons. During the larval stages, the postembryonic lineage cells are developmentally arrested in a partially differentiated state (Booker and Truman, 1987a) and do not express transmitter immunoreactivity at this time. Their maturation resumes with the onset of metamorphosis.
Plasticity in the nervous system of adult hydra. III. Conversion of neurons to expression of a vasopressin-like immunoreactivity depends on axial location
Authors: Koizumi O , Bode HR
Published: March 2018

The nervous system of hydra consists of a nerve net that extends throughout the animal. Because of the tissue dynamics of hydra, the nerve net is in a steady state of production and loss of neurons. Neurons are continuously produced in the body column and are constantly lost by sloughing at the extremities and into developing buds. Consequently, every neuron is continuously displaced towards an extremity. A subset of the neurons of the nerve net, termed vasopressin- like-immunoreactive (VLI+) neurons, has been identified with an antiserum against vasopressin. This subset has a specific regional distribution in that it is found in the head, peduncle, and foot of an adult hydra. The VLI+ neurons in the head and peduncle are ganglion cells, while those in the foot include a newly described sensory cell. How is the regional distribution of the subset maintained when every neuron is continually changing location? Removal of the neuron precursors indicates the VLI+ neurons can arise by conversion from VLI- neurons of the body column. In the normal animal they probably arise by conversion as well as by differentiation. Conversion of VLI- to VLI+ neurons is due to a change in axial position, or region, instead of a maturation process.
Bursting-induced epileptiform EPSPs in slices of piriform cortex are generated by deep cells
Authors: Hoffman WH , Haberly LB
Published: March 2018

Previous study revealed that bursting activity generated by a variety of means in slices of piriform cortex induces persistent epileptiform EPSPs in superficial pyramidal cells by an NMDA-dependent process. The present study was undertaken to test the hypothesis that the observed epileptiform EPSPs in superficial pyramidal cells are driven by deep cells. This hypothesis was suggested by recent findings from in vitro studies of the properties of deep cells and in vivo studies indicating that the deep part of the piriform cortex or neighboring deep structures are involved in the generation of seizure activity in animal models of epilepsy. Results from simultaneous cell-pair recordings, examination of subdivided slices, and local application of excitatory and inhibitory agents provided strong evidence in support of this hypothesis. It was concluded that the endopiriform nucleus, a collection of cells immediately deep to the piriform cortex, plays a central role in generation, but that cells in the deep part of layer III and the claustrum may also contribute. Furthermore, it was found that generation of prolonged ictal-like activity only occurs in slices of piriform cortex in which the endopiriform nucleus is present. Implications of these findings for epileptogenesis are discussed.
Social status in pairs of male squirrel monkeys determines the behavioral response to central oxytocin administration
Authors: Winslow JT , Insel TR
Published: March 2018

Oxytocin, when administered centrally, has been associated with the modulation of various social initiatives including maternal and sexual behaviors. The nature of these effects depends on gonadal hormone status. In the present experiments, we investigated the effects of centrally administered oxytocin on the behavior of pair-housed male squirrel monkeys during interactions with a familiar female monkey. Pairs of male squirrel monkeys established reliable and persistent dominance relationships with dominant males showing increased sexual and aggressive behavior as well as higher plasma concentrations of testosterone. Oxytocin (0.1, 1.0 micrograms) increased the sexual and aggressive behavior of dominant monkeys without affecting these measures in the subordinate monkeys. In contrast to these effects in the dominant monkeys, oxytocin increased associative and marking behaviors only in subordinate monkeys. Central administration of the oxytocin receptor antagonis d(CH2)5 [Tyr(Me)2, Thr4,Tyr-NH2(9)] OVT (OTA; 0.05 microgram) had no intrinsic effect on behavior but blocked the effects of exogenous oxytocin. To investigate further the specificity of oxytocin's effects on social behavior, we administered the structurally related peptide arginine vasopressin under identical conditions. Vasopressin (0.5, 5.0 micrograms) decreased social behaviors and increased motor activity in both dominant and subordinate monkeys. Previous studies in rodents have demonstrated that oxytocin receptors are induced by gonadal steroids in a regionally specific fashion. The status-related behavioral effects of oxytocin in the squirrel monkey may reflect differences in brain oxytocin receptor density associated with the higher concentrations of testosterone in the dominant animal. Alternatively, the status-related effects may depend on the conditioned behavioral differences associated with social organization.
Immunohistochemical localization of an inositol 1,4,5-trisphosphate receptor, P400, in neural tissue: studies in developing and adult mouse brain
Authors: Nakanishi S , Maeda N , Mikoshiba K
Published: March 2018

The immunohistochemical localization of P400/inositol 1,4,5- trisphosphate (InsP3) receptor protein was studied in developing and adult mouse brain by using monoclonal antibodies. The developmental expression pattern of P400/InsP3 receptor protein differed among different classes of neurons. It was first detected in the somata of immature Purkinje cells at embryonic day 17, in the ventrolateral region of the posterior vermis in the cerebellum. Axonal immunoreactivity within the cerebellar nuclei was first present at postnatal day 3. Neurons in the retrosplenial cortex, the anterior olfactory nucleus, and the CA1 region of the hippocampus expressed immunoreactivity earlier than other regions of the brain. In the adult brain, not only the Purkinje cell but also many other types of cells in many areas of the brain expressed P400/InsP3 receptor, though to a lesser extent. These included the neurons in the striatum, globus pallidus, nucleus accumbens septi, anterior olfactory nucleus, olfactory tubercle, precommissural hippocampus, hippocampus, substantia nigra, cerebral cortex, pons, and certain hypothalamic nuclei. Forebrain cortical regions that receive afferents from the olfactory bulb, such as the anterior olfactory nucleus, olfactory tubercle, prepiriform cortex, entorhinal cortex, and amygdala, exhibited distinct immunoreactivity, while olfactory bulb was almost devoid of staining. Immunoreactivity in the axonal pathways was also found in the limbic- hypothalamic pathways, strionigral projection, and part of the corpus callosum. Results of Western blot analysis and 3H-InsP3 binding assay were consistent with the qualitative regional differences of immunoreactivity demonstrated by immunohistochemical study. The location of InsP3 receptor in the brain correlates well with the InsP3 binding sites demonstrated by an autoradiographic study.
Glutamate and aspartate immunoreactivity in hypothalamic presynaptic axons
Authors: van den Pol AN
Published: March 2018

Within the hypothalamus, a large number of neuroactive substances are found, many first detected in this part of the brain. Excitatory amino acids, recognized as important transmitters in other parts of the brain, have received little attention here. To study glutamate immunoreactivity at the ultrastructural level in the hypothalamus, postembedding colloidal gold or silver-intensified gold was used. Antisera raised against glutamate conjugated with glutaraldehyde to keyhole limpet hemocyanin were specific for glutamate, tested with a battery of tests including immunodot blot, ELISA assays. Western blot, and Sepharose epoxy-conjugated amino acids. Antisera did not cross- react with other amino acids and related compounds, with proteins containing glutamate, or with polyglutamate. A population of presynaptic boutons in the suprachiasmatic, arcuate, ventromedial, supraoptic, and parvocellular and magnocellular paraventricular nuclei showed strong immunoreactivity for glutamate. Highly labeled presynaptic axons generally made asymmetrical Gray type 1 synaptic contacts with dendrites or cell bodies and had up to eight times more immunogold particles per unit area than postsynaptic dendrites. Axon terminals exhibiting strong glutamate immunoreactivity had large numbers of round, clear vesicles adjacent to the synaptic specialization together with a few larger, dense-core vesicles. The largest number of gold particles over axons were located in regions containing the small clear vesicles. Axons in general had about three times more gold particles over them than did the postsynaptic dendrites. Staining of single boutons in adjacent serial ultrathin sections with glutamate or GABA antisera showed that non-GABAergic terminals had a higher level of glutamate staining than did axons immunoreactive for GABA. In control experiments, immunostaining with glutamate antiserum could be blocked by solid-phase absorption of the antiserum with glutamate conjugated with glutaraldehyde to proteins. Aspartate was also detected with immunocytochemistry in some presynaptic boutons in the medial hypothalamus. To compare the response of neurons to aspartate and glutamate, calcium-imaging dyes were used in combination with digital video microscopy. Whereas almost all neurons showed a rise in intracellular Ca2+ in response to glutamate, many but not all of the same cells also showed a Ca2+ rise of smaller magnitude in response to aspartate. These ultrastructural immunocytochemical data, taken in conjunction with biochemical and electrophysiological experiments, suggest that glutamate, and to a lesser extent aspartate, may play an important neurotransmitter role in a wide variety of hypothalamic circuits.