bluuebunny/crossref_metadata_2025 huggingface dataset:
Remodeling of B-50 (GAP-43)- and NSE-immunoreactive mucosal nerves in the intestines of rats infected with Nippostrongylus brasiliensis
Authors: Stead RH , Kosecka-Janiszewska U , Oestreicher AB , Dixon MF , Bienenstock J
Published: April 2018

Intestinal mucosal mast cells (IMMCs) are closely apposed to nerves, which is consistent with other evidence suggesting that mast cells are innervated. Recent studies have indicated that coordinated changes in mast cell and nerve densities occur in the gut mucosa, during progressive fibrosis, but there is a lack of experimental evidence to support remodeling of intestinal nerve fibers as part of a disease process. Infection of rats with the nematode Nippostrongylus brasiliensis (Nb) results in an initial loss of stainable IMMCs, during an acute inflammatory phase, with subsequent mast cell hyperplasia. Accordingly, we employed the Nb model to look for structural neuroplasticity of intestinal mucosal nerves during inflammation. Immunocytochemical labeling of neurofilament subunits was very low in the jejunal mucosa of all animals, whereas neuron-specific enolase (NSE)-immunoreactive nerves were relatively abundant in control animals. The number of NSE-immunoreactive profiles increased approximately 2.5-fold by day 10 (d10) postinfection (p less than 0.01) and returned to near control values by d14. Immunoreactivity for B- 50/GAP-43 was more extensive, labeling more than four times the number of nerves per villus, compared with NSE (p less than 0.0001). B-50 immunoreactivity decreased minimally (ca. 20%) by d7 postinfection, and then increased through control values between d10 and d21, to 30% greater than controls at d49 (p less than 0.05). Subclassification of the B-50-immunoreactive nerves according to cross-sectional area revealed a greater than twofold increase in the proportions of large fibers at d7 and d10. Subsequently, the proportions of small nerves were increased compared with controls. The fiber size changes were found to correlate with mast cell densities (r = -0.72 for large and r = 0.76 for small nerves). At d10, dilated B-50- and NSE-immunoreactive nerves predominated, and extraneuronal NSE was noted. Electron microscopy revealed that this was due to axonal dilation and degeneration. These data provide evidence for plasticity of intestinal mucosal nerve fibers during inflammation. This includes early degenerative and later regenerative phases that appear to correlate with mast cell densities. The phenotype of mucosal nerves in control animals suggests ongoing modeling of these fibers.
Vacuous jaw movements and feeding deficits in rats with ventrolateral striatal dopamine depletion: possible relation to parkinsonian symptoms
Authors: Jicha GA , Salamone JD
Published: April 2018

A series of experiments examined the effects of regional dopamine depletions produced by intrastriatal injections of 6-hydroxydopamine on voluntary and involuntary movements in rats. Depletion of dopamine in the ventrolateral striatum produced a substantial decrease in food intake, from which the animals recovered. Rats with dopamine depletions in anteroventromedial or dorsolateral striatum did not have significant feeding deficits. Rats with ventrolateral dopamine depletions showed no deficits in locomotor activity or rearing behavior; however, depletions of dopamine in dorsolateral striatum significantly reduced rearing. Vacuous jaw movements that resemble chewing were produced by dopamine depletion in the ventrolateral striatum, but not the anteroventromedial or dorsolateral striatum. Systemic administration of haloperidol (0.4 mg/kg) increased vacuous chewing responses in dopamine-depleted and control rats. Thus, vacuous chewing responses can result from reduced functional activity of striatal dopamine, and these responses share some characteristics with human parkinsonian symptoms. In addition, these data support the notion that the neostriatum is functionally heterogeneous and that the ventrolateral region is particularly important for oral motor control.
Influence of spinal cord stimulation on the innervation pattern of muscle fibers in vivo
Authors: Fournier Le Ray C , Fontaine-Perus J
Published: April 2018

In chick embryo, chronic stimulation of the brachial spinal cord at a fast rhythm from days 7 to 18 of development induced an increase in AChE activity sites and ACh receptor (AChR) clusters in slow anterior latissimus dorsi (ALD) muscle. Most AChR clusters and AChE spots were contacted by nerve endings. A previous study showed that such spinal cord stimulation causes changes in ALD muscle properties, especially the appearance of a high proportion of fast type II fibers (Fournier Le Ray et al., 1989). Analysis of the synaptic pattern in different fiber types of experimental ALD muscle indicated a decrease in the distance between successive AChE spots in slow type III fibers compared to controls, whereas the intersynaptic distance in fast type II fibers was very similar to that in the rare fast fibers developing in control ALD. Fast fibers of experimental muscles exhibited less AChR than did slow fibers. The increased number of neuromuscular junctions in ALD muscle after spinal cord stimulation appeared to be preferentially located in slow fibers. Electron microscopy showed no change in the number of axons in ALD nerve after spinal cord stimulation. The activity imposed on brachial motoneurons apparently caused terminal sprouting of ALD nerve in target muscle, thus accounting for the increase in neuromuscular contacts in ALD muscle fibers. Differences in the distribution of nerve contacts indicate that the type of muscle fiber innervated may play a critical role in the synaptic pattern during chick embryogenesis.
Antagonism of central growth hormone-releasing factor activity selectively attenuates dark-onset feeding in rats
Authors: Vaccarino FJ , Feifel D , Rivier J , Vale W
Published: April 2018

Exogenous growth hormone-releasing factor (GRF) has been shown to activate feeding by central mechanisms involving the suprachiasmatic nucleus/medial preoptic area (SCN/MPOA). Until now, however, the role played by endogenous GRF in the SCN/MPOA in naturally occurring eating has remained unknown. To investigate this, the effects of SCN/MPOA injections of GRF antiserum (AS-GRF) on feeding in rats were studied. In light of SCN involvement in the control of circadian rhythms, AS-GRF was tested during the light and dark phases of the photoperiod. Results indicated that AS-GRF significantly attenuated dark-onset feeding but had no effect on feeding during the mid-dark, mid-light, or light-onset periods. These results suggest that endogenous GRF does play a role in naturally occurring feeding and that it may be involved in the circadian organization of feeding.
Changes in the distribution of extracellular matrix components accompany early morphogenetic events of mammalian cortical development
Authors: Sheppard AM , Hamilton SK , Pearlman AL
Published: April 2018

As a step in defining the molecular environment for development of the mammalian cerebral cortex, we have used immunohistochemistry to analyze the distribution and remodeling of three major extracellular matrix (ECM) components, fibronectin, chondroitin sulfate proteoglycan (CSPG), and tenascin, during embryonic and early postnatal stages in the mouse. Fibronectin and CSPG are distributed throughout the proliferative zone that initially comprises the thin wall of the telencephalic vesicle, but their distribution changes as newly generated cells form the preplate just beneath the pia. Immunolabeling for CSPG becomes most prominent in the preplate, and fibronectin becomes restricted to that layer. Just after this change occurs, processes of preplate neurons, visualized with antibodies to neurofilaments, become evident within the matrix-rich preplate zone. The association of fibronectin and CSPG with preplate cells persists as cortical plate neurons divide the preplate; both ECM components are now most prominent in the marginal zone and subplate, the layers above and below the cortical plate that are preplate derived. Within the preplate and its derivatives, immunolabeling of fibronectin is punctate and closely associated with radial glial processes, while labeling of CSPG is more intense and diffuse. Labeling of fibronectin and CSPG declines rapidly as the cortical plate begins to differentiate into cortex; labeling for tenascin first appears at this stage in the most mature layers, the marginal zone and subplate, then gradually becomes widespread throughout all of cortex and subcortical white matter. In early postnatal life, tenascin is eliminated from the hollows of the vibrissal barrels in the somatosensory region; it then declines rapidly throughout cortex. The association of both fibronectin and CSPG with preplate cells and the distribution of fibronectin along radial glia during early cortical development suggest that one or both of these transient cell types might produce specific ECM components or induce their local deposition. The spatial and temporal distribution of fibronectin and CSPG suggests a role in defining a destination for migrating neurons that form the cortical plate and in delineating the pathway for early axonal extension. In contrast, the relatively late appearance of tenascin correlates best with the formation of astrocytes and their processes rather than with the establishment of cortical layers or major axonal pathways. These events are well underway before labeling of tenascin is evident.
Pre- and postnatal development of GABA receptors in Macaca monkey visual cortex
Authors: Shaw C , Cameron L , March D , Cynader M , Zielinski B , Hendrickson A
Published: April 2018

GABA is a putative inhibitory neurotransmitter in adult mammalian visual cortex but also has been implicated as playing a crucial role in cortical information processing during development. In order to understand better the role of GABA during primate visual cortex development, we have examined the time course of GABAA and GABAB receptor ontogenesis in 18 Macaca nemestrina monkeys ranging from fetal day 61 (F61d) to adulthood. The GABA and benzodiazepine binding sites of the GABAA receptor were detected by 3H-muscimol (3H-MS) and 3H- flunitrazepam (3H-FZ), respectively. GABAB receptors were detected by 3H-baclofen (3H-BA). All ligands were visualized by in vitro autoradiography. Quantitative analysis of film density was done to compare laminar changes during pre- and postnatal development. Saturation binding experiments were done for MS and FZ binding sites to determine receptor number (Bmax) and affinity (Kd) at selected pre- and postnatal ages. Both MS and FZ binding sites were present at F61d-72d throughout the cortical plate and marginal zone. FZ binding sites were more dense than MS binding sites over the cortical plate at young ages and were especially dense over the marginal zone. FZ binding sites also were present in lesser amounts over the subplate and intermediate zone, but not over the subventricular zone. By F119d-126d, layer 4 could be distinguished by its higher density for both ligands. The basic adult laminar pattern was established for both MS and BZ binding sites by birth (birth = F165d-170d). After birth, MS density increases dramatically in all layers, but layer 4C remains most dense to adulthood. FZ labeling is heavy in both layers 4 and 3 at birth but after 4 weeks after birth (P4 wk) it declines somewhat in the supragranular layers so that layer 4C now predominates. Labeling in layers 5/6 virtually disappears after birth. BA binding sites were present at F126d, at which time layer 4 was slightly lighter than the remainder of striate cortex; this laminar pattern remained basically the same throughout our series to adulthood. Competitive binding of agonist and antagonists for the GABAA receptor showed that MS binding characteristics were similar at F126d and P8.5 years (yr). MS binding site Bmax was about 8% of adult values at F72d, 24% by F126d, and 56% at F152d. Bmax then rose rapidly after birth to peak at P18wk at 169% of adult values, and then declined to P1yr. A second peak of 143% was found around P3.5yr, with adult values reached by P8.5yr.(ABSTRACT TRUNCATED AT 400 WORDS)
A catecholaminergic sensory neuron phenotype in cranial derivatives of the neural crest: regulation by cell aggregation and nerve growth factor
Authors: Katz DM
Published: April 2018

Tyrosine hydroxylase (TH) is transiently detectable in cells distributed throughout cranial sensory ganglia during early stages of gangliogenesis [embryonic day (E) 10.5-15.5]. Although TH cells appear in embryonic ganglia of both neural crest and placode origin, mature cranial sensory neurons that express catecholaminergic properties are restricted to placode derivatives. The mechanism(s) underlying the loss of TH expression in crest-derived sensory ganglia is unknown, and the present study was undertaken to define the temporal regulation of this phenotype. Our data indicate that transient TH cells belong to a large subset of primary sensory neurons that exhibit the capability to express TH throughout development. The lack of TH expression after E15.5 appears to be due to modulation of this catecholaminergic potential. The phenotype reappears, however, when E16.5 and older ganglia are dissociated in culture into single cells, suggesting that factors associated with cell aggregation modulate TH expression. In support of this hypothesis, sensory neurons grown at high cell density exhibit lower levels of TH expression than low-density cultures. The decrease in TH levels seen at high density was associated with changes in sensory neuron morphology that are characteristic of ganglion cell maturation in vivo; therefore, modulation of TH expression may be only one facet of a more general program of sensory neuron differentiation associated with cell aggregation in developing ganglia. In contrast to the effects of cell aggregation, treatment with NGF increased the proportion of TH cells in dissociate cultures of E14.5 and E16.5 cranial sensory ganglia. Our findings indicate that sensory transmitter phenotype may be modulated by multiple factors during gangliogenesis, including cellular interactions intrinsic to the developing ganglionic microenvironment.
Modulation of calcium-activated chloride current via pH-induced changes of calcium channel properties in cone photoreceptors
Authors: Barnes S , Bui Q
Published: April 2018

The activity of calcium-activated chloride channels is controlled through the complex interaction of cellular mechanisms affecting calcium entry, buffering, and extrusion, and an unknown stoichiometric relation between intracellular Ca concentration and Cl channel activation. Here, we show that calcium-activated chloride current [ICl(Ca)] in cone photoreceptors is also highly sensitive to external pH, being strongly reduced by acidification and enhanced by alkylinization of the bathing medium. We propose that this modulation is accounted for by the pH sensitivity of Ca channel activation and permeation, already well characterized in other cells, which we now extend to cone photoreceptor Ca channels. Acidification of the external medium from a control pH of 7.4 shifts the Ca channel activation range positively by about 10 mV at pH 6.8, reducing the magnitude of calcium current with a consequent reduction of chloride current. Alkylinization shifts the Ca channel activation range negatively by about 8 mV at pH 8 and produces larger calcium currents during step depolarizations that in turn elicit larger chloride tail currents. Modulation of ICl(Ca) by pH suggests other consequences of the pH-induced shift in Ca channel gating, for one, modification of Ca-dependent transmitter release, which could be especially significant in photoreceptors where the cell's operating voltage range overlaps only the lower end of the Ca channel activation range.
A unique Kex2-like endoprotease from Drosophila melanogaster is expressed in the central nervous system during early embryogenesis
Authors: Hayflick JS , Wolfgang WJ , Forte MA , Thomas G
Published: April 2018

Complementary DNA sequences were cloned from a Drosophila library encoding a 1,101 amino acid polypeptide that we have named dKLIP-1. The deduced protein is structurally similar to the yeast KEX2 prohormone endoprotease including the conserved Asp, His, and Ser catalytic triad residues characteristic of the subtilisin family. When coexpressed in vivo with pro-beta-NGF, dKLIP-1 greatly enhanced the endoproteolytic conversion of the precursor to mature beta-NGF by cleavage at a -Lys- Arg- doublet. In adults, dKLIP-1 transcripts were detected in cortical regions of the CNS and fat body. Most striking, however, was the high level of maternal transcripts deposited into developing oocytes. The temporal and spatial expression of dKLIP-1 mRNAs during embryonic development indicates a potential role for this novel Kex2p-like endoprotease in early embryogenesis and neurogenesis.
Distribution of calbindin D28k-like immunoreactivity (LI) in the monkey ventral horn: do Renshaw cells contain calbindin D28k-LI?
Authors: Arvidsson U , Ulfhake B , Cullheim S , Ramirez V , Shupliakov O , Hokfelt T
Published: April 2018

By use of indirect immunofluorescence and peroxidase-antiperoxidase immunohistochemistry, we show that the monkey (Macaca fascicularis) ventral horn harbors small- to medium-sized neurons in lamina VII as well as a dense network of fibers in laminae IX and VII that contain calbindin D28k (calbindin)-like immunoreactivity. The highest frequency of immunoreactive (IR) cell bodies was found at the levels of the cervical and lumbar intumescences. Furthermore, rostrocaudally oriented calbindin-IR fibers were encountered in the ventral and ventrolateral funiculi throughout the whole length of the cord, with the highest density at cervical and lumbar intumescences. Analysis at the EM level revealed calbindin-IR terminals in contact preferentially with dendrites of variable size and occasionally also large cell bodies, presumably belonging to motoneurons, in the lateral motor nucleus. The location of calbindin-IR neurons, as well as the distribution and ultrastructural characteristics of the calbindin-IR axonal system, makes it highly likely that these neurons are Renshaw cells that mediate recurrent inhibition to motoneurons.
An actin-associated protein present in the microtubule organizing center and the growth cones of PC-12 cells
Authors: Bearer EL
Published: April 2018

The pathfinding ability of the growth cone depends upon the integrity of a dynamic actin filament network. However, although a number of actin-binding proteins have been found in growth cones, it is not known how these proteins come to be concentrated there or how they might interact to produce these important actin filaments. In this report, an actin-associated protein recognized by the monoclonal antibody 2E4 is demonstrated to be present in PC-12 cells. In undifferentiated cells, this protein is present in an apparently inactive state in a perinuclear location that corresponds to that of the microtubule organizing center and not of the Golgi apparatus. Conversely, after NGF- induced differentiation, the antigen is found enriched in the neurite and growth cone and disappears from the perinuclear position. This disappearance is directly proportional to the length of the neurite. The antigen-antibody complex binds the ends of actin filaments in vitro in an ATP-sensitive manner, and the antibody stains the outermost edge of the actin filament ruffle in the leading edge of migrating fibroblasts. Hence, it is possibly involved in the membrane-associated polymerization of actin filaments such as that observed in growth cones.
Beta-adrenergic receptors: astrocytic localization in the adult visual cortex and their relation to catecholamine axon terminals as revealed by electron microscopic immunocytochemistry
Authors: Aoki C
Published: April 2018

It has long been recognized that noradrenaline, the most abundant catecholamine within the visual cortex, plays important roles in modulating the sensitivity of cortical neurons to visual stimuli. However, whether or not these noradrenaline effects are confined to a discrete synaptic specialization or mediated by diffuse modulation of a group of synapses has remained an issue open for debate. The aim of this study was to examine the cellular basis for noradrenaline action within the visual cortex of adult rats and cats. To this end, I used electron microscopic immunocytochemistry to examine the relationship between (1) catecholamine axon terminals and beta-adrenergic receptors (beta AR), which, together, may define the effective sphere of noradrenaline modulation; and then (2) these putative sites for catecholamine modulation and axospinous asymmetric junctions where excitatory neurotransmission is likely to dominate. Antibodies against beta AR were used at light and electron microscopic levels on the visual cortex of rat and cat. Rat visual cortex was also labeled simultaneously for beta AR and the catecholamine-synthesizing enzyme, tyrosine hydroxylase (TH), to determine the ultrastructural relationships between catecholamine terminals and beta AR. Immunoperoxidase labeling revealed that beta AR404, a polyclonal antibody directed against the C-terminal tail of hamster lung beta AR (beta 2-type), recognized astrocytic processes predominantly. In contrast, beta AR248, a polyclonal antibody directed against the third cytoplasmic loop, recognized neuronal perikarya as observed in previous studies. Dual labeling for beta AR404 and TH revealed that catecholamine axon terminals that contained numerous vesicles formed direct contacts with astrocytic processes exhibiting beta AR404 immunoreactivity. However, some catecholamine axon terminals that lacked dense clusters of vesicles were positioned away from beta AR404- immunoreactive astrocytes. Frequently, beta AR-immunoreactive astrocytic processes surrounded asymmetric axospinous junctions while also contacting catecholamine axon terminals. These observations support the possibility that, through activation of astrocytic beta AR, noradrenaline modulates astrocytic uptake mechanism for excitatory amino acids, such as L-glutamate. Astrocytic beta AR might also define the effective sphere of catecholamine modulation through alterations in the morphology of distal astrocytic processes and the permeability of gap junctions formed between astrocytes.
Responses of human mechanoreceptive afferents to embossed dot arrays scanned across fingerpad skin
Authors: Phillips JR , Johansson RS , Johnson KO
Published: April 2018

The spatial resolving capacities of the four classes of mechanoreceptive afferents innervating human fingerpad skin were investigated to determine which class sets the limit of tactile spatial resolution for scanning stimuli. The stimulus consisted of an array of embossed dots (0.7 mm diameter, 0.5 mm high) arranged in a tetragonal pattern with dot spacing decreasing linearly from 6.4 mm at one end of the array to 0.87 mm at the other. The pattern was wrapped around a drum and repeatedly scanned across the receptive field of single afferents by continuously rotating the drum. Responses to many closely spaced scans were obtained by imposing a lateral shift of the pattern between each revolution. Impulses were recorded microneurographically. Responses were plotted in raster form to produce a neural image of the pattern. Responses of rapidly and slowly adapting type I (FAI and SAI) afferents resolved dots down to a spacing of about 1.5 mm. Responses of type II (FAII and SAII) afferents resolved dots down to a spacing of about 3.5 mm. Variation in scanning speed (range, 20–90 mm/sec) and contact force (range, 0.4–1.0 N) had minimal effects on spatial resolution of all afferents. The response clusters associated with individual widely spaced dots were used to investigate receptive field structure. FAI and SAI fields (mean areas, 6.1 and 4.8 mm2, respectively) each contained several zones of maximal sensitivity. FAI fields had five to eight such zones, whereas SAI fields had three to five such zones. As dot spacing decreased, neighboring dots interacted to affect the responses associated with the individual zones within a field. Initially, one or more zones were deactivated, effectively reducing receptive field size and allowing representation of finer spatial detail than would be predicted from the overall area of the receptive field. At very close dot spacings responses were only obtained when more than one sensitive zone within a field were simultaneously activated by different dots.
Alternative splicing of micro-exons creates multiple forms of the insect cell adhesion molecule fasciclin I
Authors: McAllister L , Rehm EJ , Goodman GS , Zinn K
Published: April 2018

Fasciclin I is a homophilic cell adhesion molecule in insects that is dynamically expressed on a subset of axon pathways in the embryonic nervous system, and on a variety of other cells and tissues during development. The fasciclin I protein consists of four homologous 150 amino acid domains. In this article, we describe the complete sequence of the Drosophila fasciclin I (fasI) gene. The gene consists of 15 exons and is distributed over 14 kilobases of DNA. We examine the structure and temporal expression pattern of multiple fasciclin I mRNAs that differ in the lengths of their 3′ untranslated regions. We also show that a highly conserved sequence at the end of the second domain can be altered by the addition of three or six amino acids that are encoded by two alternatively spliced 9 base pair (bp) micro-exons. In grasshopper fasciclin I mRNAs, there are 9 bp and 6 bp insertions at the same position. The first of these insertions is identical in sequence to the first fly micro-exon. The grasshopper insertions are not found together in the same mRNA, so grasshopper fasciclin I species differ by the addition of three or two extra amino acids to the second domain. The alternatively spliced mRNAs are differentially expressed during embryogenesis, and all three of them are present in nerve cord preparations. We suggest that the amino acids inserted by alternative micro-exon splicing may alter the binding specificity of fasciclin I.
Pharmacological discrimination of N-type from L-type calcium current and its selective modulation by transmitters
Authors: Cox DH , Dunlap K
Published: April 2018

GABA and norepinephrine inhibit high voltage-activated calcium current in chick sensory neurons. Using specific pharmacological tools, we have dissected this current into two components: the major one is omega- conotoxin sensitive and dihydropyridine resistant (N-type) while the minor one is dihydropyridine sensitively and omega-conotoxin resistant (L-type). The ability to selectively eliminate these two components has allowed us to determine whether the transmitters target the same or different channel types. Both GABA and norepinephrine modulate the N- type component as evidenced by their lack of effect on (1) omega- conotoxin-resistant current and (2) pure L-type tail current, prolonged by a dihydropyridine calcium channel agonist. This simple pharmacological profile will allow future tests of the significance of the two channel types in regulating sensory neuron functions.
Pentamidine is an N-methyl-D-aspartate receptor antagonist and is neuroprotective in vitro
Authors: Reynolds IJ , Aizenman E
Published: April 2018

Acquired immunodeficiency syndrome (AIDS) is frequently associated with dementia. The wide spectrum of neurological abnormalities associated with this dementia may involve a neurotoxin that activates the NMDA subtype of glutamate receptor in neurons. We have found that the antimicrobial agent pentamidine, which is prescribed for AIDS patients for the prophylaxis and treatment of Pneumocystis carinii pneumonia, is an effective NMDA receptor antagonist. Pentamidine inhibited 3H- dizocilpine binding to the NMDA receptor in rat brain membranes at a site separate from glutamate, glycine, and spermidine, with an affinity near 2 microM. Similar concentrations of pentamidine block NMDA-induced increases in intracellular Ca2+ and NMDA-induced currents in cultured forebrain and cortical neurons, apparently without use dependence or voltage dependence, suggesting that pentamidine may represent a novel chemical class of NMDA receptor antagonist. Finally, pentamidine protects neurons from the lethal effects of acute NMDA exposure in vitro. AS pentamidine may accumulate in the brain at relevant concentrations following repeated high-dose parenteral administration, these findings suggest that the drug may be neuroprotective in vivo.
Molecular cloning and development analysis of a new glutamate receptor subunit isoform in cerebellum
Authors: Gallo V , Upson LM , Hayes WP , Vyklicky L , Winters CA , Buonanno A
Published: April 2018

The glutamate receptor gene GluR-4 is proposed to generate two spliced isoforms (Sommer et al., 1990). Screening a rat cerebellar cDNA library, we have now identified a third type of transcript derived from GluR-4 gene by differential RNA processing. This transcript encodes a protein with a “flop” module between transmembrane regions 3 and 4, but with a C-terminus segment of 36 amino acids different from the previously described GluR-4 flip/flop cDNAs. This subunit was therefore designated as GluR-4c flop. Transcripts synthesized in vitro from GluR- 4c cDNA form kainate/AMPA-activated channels when expressed in Xenopus oocytes. The current-voltage relationship for kainate-evoked responses in oocytes injected with GluR-4c showed strong inward rectification. The different transcripts derived from the GluR-4 gene were studied on Northern blots hybridized with either a cDNA probe or oligonucleotides specific for the GluR-4 flip/flop and C-terminal domains. Three transcripts of 6.2, 4.2, and 3.0 kilobases (kb) derived from the GluR-4 gene were identified on Northern blots containing total RNA prepared from different brain regions, using a cDNA probe or an oligonucleotide corresponding to the N-terminal region common to all transcripts. These transcripts were much more abundant in the cerebellum than in other brain areas, and their levels increased during cerebellar development. The maximal increase was observed between postnatal days 1 and 20, an age corresponding to the division and maturation of granule neurons. The flip/flop and the C-terminal oligonucleotides hybridized to the two higher molecular weight transcripts but did not hybridize to the small RNA. Interestingly, using cerebellar cells that were cultured for up to 12 d, we observed that the three transcripts are present in granule neurons, but that astrocytes only express the 6.2 and the 4.2 kb transcripts. The 3.0 kb transcript accumulates in cerebellar granule cells during development in vitro. Furthermore, in situ hybridization histochemistry revealed that the GluR-4c transcripts are preferentially expressed in cerebellar granule cells and Bergmann glial cells, whereas the expression of GluR-4 flip mRNAs is restricted to Bergmann glial cells. Interestingly, we also show that granule cells already express GluR-4c in the premigratory zone of the external granular layer, indicating that intrinsic or highly localized cues induce GluR-4c expression before these cells reach their final position.
Oxytocin and vasopressin release in discrete brain areas after naloxone in morphine-tolerant and -dependent anesthetized rats: push-pull perfusion study
Authors: Russell JA , Neumann I , Landgraf R
Published: April 2018

The effects of naloxone on the release of oxytocin and vasopressin in discrete brain areas were investigated in control and morphine- tolerant/dependent female rats anesthetized with urethane. Two or three consecutive push-pull perfusates were collected for 30–40 min each and the peptide contents measured by radioimmunoassay; naloxone (5 mg/kg, i.v.) was given after the first perfusion. In control rats, naloxone did not increase oxytocin release from any of the regions studied: mediolateral septum, dorsal hippocampus, nucleus of tractus solitarius, or supraoptic nucleus. After naloxone, vasopressin release was approximately doubled in the nucleus of tractus solitarius (p less than 0.05), indicating endogenous opioid inhibition of vasopressin release. Naloxone increased oxytocin concentration in the circulation 3.7-fold (p less than 0.001) but did not affect vasopressin secretion. In rats made morphine tolerant/dependent by intracerebroventricular infusion of morphine for 5 d, oxytocin and vasopressin release in the perfused brain was initially similar to that in control rats, indicating tolerance to any initial morphine effects. In these rats, naloxone increased oxytocin release in the septum threefold relative to control rats (p less than 0.02) but did not alter oxytocin release in hippocampus or nucleus of tractus solitarius. Thus, the oxytocin neurons projecting to septum can develop morphine dependence and may be inhibited acutely by opioids acting via mu-receptors. The results indicate morphine acts selectively on oxytocin neurons projecting to mediolateral septum compared with other central projection areas and compared with centrally projecting vasopressin neurons. In the supraoptic nucleus, naloxone increased oxytocin release 2.3-fold (from 9.2 +/- 3.1 pg/30 min) and increased oxytocin release from axons of these neurons fivefold (from 7.8 +/- 3.2 pg/30 min). Naloxone had no significant effect on vasopressin release from any of the central sites, or on vasopressin secretion into blood, although oxytocin secretion was increased 36-fold (from 17.2 +/- 2.6 pg/ml; p less than 0.001), confirming dependence of magnocellular oxytocin neurons. The central processes of magnocellular supraoptic neurons may be a major source of central oxytocin released during morphine withdrawal.
Pharmacological characterization of endothelin-stimulated phosphoinositide breakdown and cytosolic free Ca2+ rise in rat C6 glioma cells
Authors: Lin WW , Kiang JG , Chuang DM
Published: April 2018

Because increasing evidence indicates that glial cells are a target of endothelin, we have characterized endothelin-induced phosphoinositide (PI) turnover and Ca2+ homeostasis in C6 glioma cells. Endothelin-1 (ET) increased formation of 3H-inositol phosphate (IP) from PI and elicited an increase in cytosolic free Ca2+ ([Ca2+]i) in rat C6 glioma. In the presence of Li+, the increase in 3H-inositol trisphosphate formation was rapid, reaching its peak at 5 min after stimulation. ET also elicited a rapid and sustained increase in [Ca2+]i in a dose- dependent manner (1–100 nM). The rank orders of efficacy for ET-related peptides in increasing [Ca2+]i were ET = ET-2 greater than sarafotoxin greater than ET-3. Both ET-mediated stimulation of IP formation and [Ca2+]i increase were largely inhibited in the absence of external Ca2+ but unaffected by the depletion of external Na+ and the presence of dihydropyridine derivatives or verapamil. Inorganic Ca2+ channel blockers Cd2+, La3+, and Mn2+ at 1 mM inhibited both responses induced by ET. Cross-desensitization and nonadditivity were observed for both events among ET-related peptides tested, but not between ET and ATP. Pretreatment of cells with pertussis toxin (PTX) attenuated the PI response to ET, but had no effect on ET-elicited [Ca2+]i increase. ET- induced Ca2+ mobilization (measured in Ca(2+)-free medium) was only transient and was inhibited by 8-(N,N-diethylamino)octyl-3,4,5- trimethoxybenzoate. Moreover, the intracellular Ca2+ pools mobilized by ET and ATP appeared to overlap, as indicated by their partial heterologous desensitization.(ABSTRACT TRUNCATED AT 250 WORDS)
Neuropeptide Y selectively inhibits slow synaptic potentials in rat dorsal raphe nucleus in vitro by a presynaptic action
Authors: Kombian SB , Colmers WF
Published: April 2018

Neuropeptide Y (NPY) has been shown to modulate synaptic transmission in both peripheral and central tissues via both pre- and postsynaptic mechanisms. In this study, we examined the effect of NPY and its analog, peptide YY (PYY), on slow synaptic potentials in the dorsal raphe nucleus in vitro using intracellular recording and single- microelectrode voltage-clamp techniques. NPY and PYY inhibited both the slow 5-HT1A receptor-mediated IPSP and the alpha 1-adrenoceptor- mediated slow EPSP while not affecting the fast, amino acid-mediated synaptic responses. PYY also inhibited pharmacologically isolated slow synaptic responses. NPY/PYY appear to mediate the observed inhibitions via a presynaptic mechanism, as the postsynaptic conductances mediated by activation of 5-HT1A receptors or alpha 1-adrenoceptors were unaffected by the peptides. NPY/PYY act via a different mechanism than presynaptic 5-HT1B receptors. NPY/PYY probably act via presynaptic Y2 receptors, as the C-terminal fragment NPY 13–36 and the Y2-selective agonist C2-NPY are effective. Since NPY and its receptors are present in the dorsal raphe nucleus, this peptide may act as an endogenous modulator of the state of activity of neurons in this region and may thus have a role in the modulation of neuronal output from this nucleus.
Cyclic AMP-dependent phosphorylation of the rat brain ryanodine receptor
Authors: Yoshida A , Ogura A , Imagawa T , Shigekawa M , Takahashi M
Published: April 2018

Phosphorylation of the rat brain ryanodine receptor was studied using a monoclonal antibody, Ry-1, against the cardiac ryanodine receptor. A large polypeptide with the same SDS-PAGE mobility as that of the canine cardiac receptor was detected in rat brain membranes by immunoblotting. The brain ryanodine receptor was solubilized from the microsomal membranes with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid (CHAPS), and more than 85% of the solubilized receptor was immunoprecipitated by Ry-1. Immunoprecipitated receptors were phosphorylated by cAMP-dependent protein kinase. The ryanodine receptor was also expressed in cultured fetal rat brain neurons and was phosphorylated by treating the cells with dibutyryl cAMP. The number of cells showing a caffeine-induced Ca2+ transient was increased significantly in the phosphorylating condition. These results suggest that the Ca channel activity of the brain ryanodine receptor is regulated by cAMP-dependent phosphorylation.
Bilateral inhibition generates neuronal responses tuned to interaural level differences in the auditory brainstem of the barn owl
Authors: Adolphs R
Published: April 2018

I investigated the neural algorithms by which neurons gain selectivity for interaural level difference in the brainstem of the barn owl (Tyto alba). Differences in the timing and in the level of sounds at the ears are used by this owl to encode, respectively, azimuthal and vertical position of sound sources in space. These two cues are processed in two parallel neural pathways. Below the level of the inferior colliculus, all neurons in the pathway that processes level differences show responses to this cue that are monotonic, and thus not selective for a particular level difference. Only in the inferior colliculus, which contains a map of auditory space, are neurons sharply tuned to specific interaural level differences. How are these response properties generated from those of the nuclei that provide input to the inferior colliculus? I show that the posterior subdivision of the nucleus ventralis lemnisci lateralis (VLVp) projects bilaterally to the lateral shell of the central nucleus of the inferior colliculus, the input stage to the map of auditory space. Both these nuclei are part of the pathway that processes interaural level differences. Manipulations of the responses in VLVp affected the responses to level differences in the inferior colliculus; responses to time differences were unaffected. By systematically increasing or decreasing neural activity in VLVp, I show that the VLVp on each side provides inhibition to the colliculus at large level differences. This results in a peaked response that is tuned to level differences in the inferior colliculus. Some cells in the lateral shell of the inferior colliculus appear to receive direct GABAergic inhibition from VLVp. I suggest that this circuitry and the algorithms it supports are the neural substrates that allow the barn owl to exploit level differences for computation of sound source elevation.
Insulin-like receptor and insulin-like peptide are localized at neuromuscular junctions in Drosophila
Authors: Gorczyca M , Augart C , Budnik V
Published: April 2018

Insulin and insulin-like growth factor (IGF) receptors are members of the tyrosine kinase family of receptors, and are thought to play an important role in the development and differentiation of neurons. Here we report the presence of an insulin-like peptide and an insulin receptor (dInsR) at the body wall neuromuscular junction of developing Drosophila larvae. dInsR-like immunoreactivity was found in all body wall muscles at the motor nerve branching regions, where it surrounded synaptic boutons. The identity of this immunoreactivity as a dInsR was confirmed by two additional schemes, in vivo binding of labeled insulin and immunolocalization of phosphotyrosine. Both methods produced staining patterns markedly similar to dInsR-like immunoreactivity. The presence of a dInsR in whole larvae was also shown by receptor binding assays. This receptor was more specific for insulin (> 25-fold) than for IGF II, and did not appear to bind IGF I. Among the 30 muscle fibers per hemisegment, insulin-like immunoreactivity was found only on one fiber, and was localized to a subset of morphologically distinct synaptic boutons. Staining in the CNS was limited to several cell bodies in the brain lobes and in a segmental pattern throughout most of the abdominal ganglia, as well as in varicosities along the neuropil areas of the ventral ganglion and brain lobes. Insulin-like peptide and dInsR were first detected by early larval development, well after neuromuscular transmission begins. The developmental significance of an insulin-like peptide and its receptor at the neuromuscular junction is discussed.
The anterior cerebellar vermis: essential involvement in classically conditioned bradycardia in the rabbit
Authors: Supple WF , Kapp BS
Published: April 2018

The effects of lesions of the cerebellum on the acquisition and retention of aversive Pavlovian conditioned bradycardia were examined in rabbits. Lesions of the anterior cerebellar vermis severely attenuated the acquisition of simple conditioned bradycardia without disrupting baseline heart rate (HR), or unconditioned HR responses. Also, lesions of the vermis performed after the acquisition of conditioned bradycardia eliminated evidence of prior conditioning. Bilateral lesions of the cerebellar hemispheres did not affect conditioned or unconditioned HR responses. These results were interpreted to indicate that anterior vermis lesions specifically disrupted part of an essential conditioned response pathway without interfering with the neural circuits that mediate unconditioned HR responding. These lesion data, coupled with recent electrophysiological evidence of learning-related changes in neuronal activity within the anterior vermis of the fear-conditioned rabbit, suggest that the anterior cerebellar vermis is critically involved in the acquisition and retention of this rapidly learned autonomic conditioned response.
Hierarchical organization of areas in rat visual cortex
Authors: Coogan TA , Burkhalter A
Published: April 2018

To test the hypothesis that areas within rat visual cortex are organized in a multilevel hierarchy, we have employed Phaseolus vulgaris leucoagglutinin as an anterograde axonal tracer to visualize the laminar patterns of connections between different cortical areas. For identification of cortical areas, we used a combination of markers that included callosal connections, the patterns of inputs and outputs to ipsilateral cortical and subcortical targets, and geographical location. Projections from area 17 to every identified extrastriate target area extend throughout all layers of cortex and include layer 4. Area LM (lateromedial), contained within the cytoarchitectonic subdivision 18a, projects to area 17, area AL (anterolateral), area RL (rostrolateral), multiple sites within the posterior complex (PX), the anterior complex (AX), the far lateral complex (FLX), the medial complex (MX), perirhinal, entorhinal, retrosplenial, and presubicular cortex. Each of the projections to extrastriate areas resembles those originating from area 17. Only the projection to area 17 differs, and terminates largely in layers outside of lamina 4. Such projections are designated as feedback (Coogan and Burkhalter, 1990). The projections of a second area, AL, of the cytoarchitectonic subdivision 18a are similar to those of LM: all terminate in layers 1–6, except the inputs to area 17, LM, and a site in FLX, which spare layer 4. The feedback projection to LM provides further support that LM and AL constitute distinct cortical areas. Projections from additional distinct sites within area 18a that are located immediately lateral to LM and AL and are designated FLX make feedback projections to area 17 and projections involving all layers to LM and AL. Thus, unlike the asymmetrical laminar organization of reciprocal connections between area 17 and LM, 17 and AL, and LM and AL, the connections between LM and at least one site in FLX are symmetrical. Projections that include layer 4 can, therefore, be components of connections between different hierarchical levels as well as components of connections on the same hierarchical level. The MX sites contained within the cytoarchitectonic subdivision 18b send feedback projections to striate cortex, LM, AL, and PX within 18a. Thus, the connections between these areas are reciprocal and the laminar organization is asymmetrical. The projections to FLX include layer 4, and the projections to frontal, cingulate, and retrosplenial cortex resemble forward projections. Although the areal organization of extrastriate cortex is not yet fully resolved, using the patterns of intracortical connections we are able to construct a provisional hierarchy of cortical areas.(ABSTRACT TRUNCATED AT 400 WORDS)
Cholinergic regulation of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) but not neurotrophin-3 (NT-3) mRNA levels in the developing rat hippocampus
Authors: da Penha Berzaghi M , Cooper J , Castren E , Zafra F , Sofroniew M , Thoenen H , Lindholm D
Published: April 2018

In previous experiments it has been demonstrated that the synthesis of BDNF (brain-derived neurotrophic factor) and NGF in neurons of the hippocampus is regulated by neuronal activity. The glutamate system is predominantly responsible for upregulation and the GABAergic system for downregulation both in vitro and in vivo (Zafra et al., 1990, 1991). The aim of the present study is to examine the extent to which the cholinergic system is also involved in the regulation of NGF and BDNF mRNA and whether the regulatory contribution of the cholinergic system changes during development. Partial transection of the fimbria fornix bundle in the second postnatal week resulted in a reduction of BDNF and NGF mRNA levels in the hippocampus, suggesting that septal cholinergic input is involved in the regulation of hippocampal BDNF and NGF mRNA levels. Because the fimbria fornix bundle also contains fibers other than cholinergic ones, we further evaluated the importance of the cholinergic influence by injecting pilocarpine, a muscarinic agonist. Pilocarpine markedly increased hippocampal BDNF and NGF mRNA levels in both early postnatal and adult rats. In situ hybridization experiments demonstrated that pilocarpine led to an increase in BDNF expression in the CA1-CA4 regions of the hippocampus and in the dentate gyrus. However, pilocarpine increased NGF mRNA only in those neurons of the dentate gyrus and CA1-CA4 regions that also expressed NGF mRNA in the controls.(ABSTRACT TRUNCATED AT 250 WORDS)