bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in 3H-substance P receptor binding in the rat brain after kainic acid lesion of the corpus striatum
Authors: Mantyh PW , Hunt SP
Published: March 2018

Previous studies have indicated that the substantia nigra contains the highest concentration of substance P-like immunoreactivity (SPLI) in the brain. Paradoxically, it also appears to contain one of the lowest concentrations of substance P receptors in the brain. One possibility is that the massive amount of SPLI blocks the binding of the radioligand to the substance P receptor and/or “down-regulates” the number of substance P receptors present in this structure. Since greater than 95% of the SPLI within the substantia nigra originates from the corpus striatum, we have lesioned this area and measured the changes in substance P receptor concentration in the substantia nigra and other corpus striatal projection areas. A semiquantitative autoradiographic technique for measuring the binding of 3H-substance P to substance P receptors was used in conjunction with tritium-sensitive film. 3H-substance P binding was measured in both the corpus striatum and its projection areas after kainic acid lesion of the corpus striatum. At either 4 or 21 d after the lesion there was approximately a 90% loss of substance P receptors in the rostral striatum, a 74% loss in the globus pallidus, a 57% increase in receptor number in lamina I and II of the ipsilateral somatosensory cortex, and no apparent change in the number of receptors in the substantia nigra pars reticulata, superior colliculus, and central gray. These findings suggest that the low concentration of substance P receptors found within the substantia nigra is not due the massive SPLI innervation, since removal of greater than 95% of the SPLI had no measurable effect on the concentration of substance P receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
5,7-Dihydroxytryptamine lesions of crayfish serotonin-containing neurons: effect on the lateral giant escape reaction
Authors: Glanzman DL , Krasne FB
Published: March 2018

The crayfish's lateral giant escape response, a relatively simple behavioral reaction, is readily modulated in certain situations. For example, when a crayfish is restrained, its lateral giant (LG) fibers-- command neurons that mediate the escape response--are strongly inhibited (Krasne and Wine, 1975). Previous work (Glanzman and Krasne, 1983) had suggested that serotonin (5-HT) might mediate this restraint- induced inhibition of the escape response. To test this possibility, we attempted to lesion serotonergic neurons in crayfish with the 5-HT neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT). We compared the levels of 5-HT-immunoreactive staining in nerve cords from 5,7-DHT-treated and from normal crayfish to assess 5,7-DHT's effectiveness. Levels of immunoreactive staining, as judged by ratings of the visibility of immunofluorescence, were significantly lower in nerve cords from crayfish that had received injections of 5,7-DHT (1.0-4.0 mg) than in nerve cords from normal crayfish. In addition, some serotonergic neurons in the neurotoxin-treated crayfish developed an abnormal brown pigmentation. To assess the behavioral consequence of central serotonergic lesions, we compared the responsiveness of escape in crayfish treated with 5,7-DHT (2.0–2.75 mg) and in normal crayfish. The threshold for firing the LGs was significantly lower in restrained neurotoxin-treated animals than in restrained normal animals. Furthermore, the responsiveness of the LGs in neurotoxin-treated crayfish approximated that in crayfish whose nerve cords had been severed between the thorax and abdomen, a procedure known to abolish restraint-induced inhibition (Krasne and Wine, 1975).(ABSTRACT TRUNCATED AT 250 WORDS)
Multielectrode analysis of coordinated, multisite, rhythmic bursting in cultured CNS monolayer networks
Authors: Droge MH , Gross GW , Hightower MH , Czisny LE
Published: March 2018

Laser-deinsulated, printed-ircuit electrodes integrated into the floor of culture chambers have been used to monitor the spontaneous activity of mouse spinal monolayer cell cultures. This technique has allowed a multisite analysis of activity over long periods of time in closed chambers. In 63 cultures investigated 3–5 weeks after seeding, 89% included single- or multiunit bursting. Based on a subset of 40 cultures in which all electrodes were sequentially scanned, bursting was found on 41% of the active electrodes (approximately 38% of all units monitored). A total of 35% of the electrodes monitoring spontaneous bursting activity revealed rhythmic sequences that were usually coupled among multiple electrodes. Although most of this coupling was in-phase, three out of 40 cultures exhibited antiphasic bursting. In all cases where coupling was observed, each electrode monitored different burst compositions, demonstrating that the activity was generated by different units. Some rhythmic patterns persisted for over 12 hr and were observed in 400 mm2 monolayer cultures, as well as in much smaller 3 mm2 adhesion islands. The addition of 10 mM MgCl2 consistently blocked both random and patterned (i.e., bursting) spontaneous activity at all recording sites. Strychnine (10(-6) M) typically increased firing frequencies and either disrupted pretest bursting or generated rhythmic activity from random phasic patterns. In certain cases, strychnine also blocked activity on specific electrodes, indicating that glycine is not the only inhibitory transmitter involved. The spontaneous appearance of rhythmic activity in low- density, monolayer cell cultures established from dissociated and randomly seeded spinal tissue can be explained by one or a combination of two hypotheses: an inherent specificity of some interconnections in developing mammalian cultures and the generation of organized activity by random circuits at certain stages of complexity.
Gradient of extrajunctional acetylcholine receptors early after denervation of mammalian muscle
Authors: Levitt-Gilmour TA , Salpeter MM
Published: March 2018

After denervation, the number of acetylcholine receptors (AChR) found within the endplate band of skeletal muscle increases transiently by about twofold. In this study, we used EM autoradiography to show that this increased endplate band label is not due to an elevated site density of receptors at the junctional folds. Rather, AChR site density within 500 microns of the endplate was found to be 4 X higher than in non-endplate areas defined as greater than 2 mm from the endplate. This nonuniform distribution of extrajunctional AChR early after denervation could represent a transient gradient,similar to that reported shortly after innervation during development.
Development and loss of early projections in a sexually dimorphic rat spinal nucleus
Authors: Sengelaub DR , Arnold AP
Published: March 2018

The spinal nucleus of the bulbocavernosus (SNB) contains 3–4 times more motoneurons in adult male rats compared to females. This large dimorphism in motoneuron number is produced perinatally by an androgen- regulated cell death. To determine if the early projections of the SNB to its target musculature may be involved in the creation of this sexual dimorphism, and how these projections might interact with androgens, HRP tracing techniques were used to retrogradely label SNB motoneurons during prenatal and postnatal development in males, females, and masculinized females. HRP labeling revealed that the prenatal formation of early projections of the SNB in males and females is comparable. SNB motoneuron number increases through the day before birth in all groups, and during this increase, labeled cells can be seen outside the SNB, which we hypothesize are in the process of migrating into the SNB from the lateral motoneuron column. Postnatally, SNB motoneuron number declines, especially in females, and by postnatal day 10 the sexual dimorphism in cell number and projections has been established. These results indicate that although masculine androgen levels are critical in determining SNB motoneuron survival, they are not necessary for initial axon outgrowth of SNB motoneurons. However, androgens may be involved in the regulation of SNB motoneuron migration and the stabilization of the peripheral projections of the SNB. Both male and female SNB motoneuron axons are present at their target muscles during the time in which sex differences in motoneuron number develop, suggesting that the interaction of SNB motoneurons with their targets could be involved in the dimorphic regulation of cell survival.
Localization of 3H-GABA, -muscimol, and -glycine in goldfish retinas stained for glutamate decarboxylase
Authors: Ball AK , Brandon C
Published: March 2018

Glutamic acid decarboxylase (GAD), the synthesizing enzyme for the neurotransmitter GABA, has been localized in goldfish retina using a new antiserum. We observed at least six types of GAD-immunoreactive amacrine cells, one of which was large and pyriform (Ab type). In addition, immunoreactive synaptic terminals were located throughout the inner plexiform layer (IPL). Amacrine cells that were GAD- immunoreactive also had high-affinity uptake mechanisms for both 3H- GABA and 3H-muscimol that were detectable autoradiographically. Type Ab pyriform amacrine cells were heavily labeled because of 3H-GABA uptake and were GAD-immunoreactive. Other types of GAD-immunoreactive amacrine cells, including a subpopulation of Ab amacrines, were lightly labeled because of 3H-GABA uptake. Because the same neurons that were GAD- immunoreactive also accumulated 3H-GABA and 3H-muscimol, these three are appropriate markers for GABAergic cells in the goldfish retina. However, the uptake of 3H-muscimol by many non-GAD-immunoreactive cells, detectable at longer autoradiographic exposure times, indicates that this label must be used with caution. Thirty percent of goldfish retinal amacrine cells are GABAergic, and their processes are distributed throughout all levels of the IPL. Few GAD-immunoreactive amacrine cells accumulated 3H-glycine, so the goldfish retina contains distinct populations of glycinergic and GABAergic amacrine cells.
Identification of the cerebral neurosecretory cells that contain eclosion hormone in the moth Manduca sexta
Authors: Copenhaver PF , Truman JW
Published: March 2018

Eclosion hormone (EH) is an insect neuropeptide that is released at the end of metamorphosis from the CNS and triggers the stereotyped motor program of adult emergence. Using three distinct experimental approaches, we have identified a discrete set of neurosecretory cells in the brain of the moth Manduca sexta that contains and releases EH. By isolating the neurosecretory somata and testing them with a sensitive behavioral bioassay, we identified a cluster of ipsilaterally projecting cells (Group Ia) that contain EH. Intracellular stimulation of individual cells within this group induced the release of bioactive EH into the hemolymph surrounding the neurohemal organs of the brain, whereas stimulation of cells in the other cerebral neurosecretory clusters did not. We also developed a polyclonal antiserum against purified EH that precipitated all bioactive material from samples containing the peptide. This antiserum selectively stained 5 of the Group Ia cells on either side of the brain, as well as their central and terminal processes. Preincubation of the serum with EH dramatically reduced its ability to bind the peptide subsequently. The combined application of these physiological and immunological techniques has led to the unequivocal identification of the EH neurons in the moth brain.
Long- and short-term monocular deprivation in the rhesus monkey: effects on visual fields and optokinetic nystagmus
Authors: Sparks DL , Mays LE , Gurski MR , Hickey TL
Published: March 2018

Monkeys with 1 eyelid sutured within 2 weeks of birth for 7 or 14 d (short-term monocular deprivation, n = 5) or for 18–26 months (long- term monocular deprivation, n = 5) were tested for visual and oculomotor function at approximately 2 years of age. Long-term monocularly deprived animals were behaviorally blind when visual inputs were restricted to the deprived eye. There was no sparing of the monocular segment of the visual field, and optokinetic nystagmus could not be elicited even with vertical stripes up to 15 degrees in width. These behavioral deficits could not be accounted for by optical or retinal abnormalities. In contrast, short-term monocularly deprived animals displayed normal visual fields and optokinetic nystagmus was driven by both eyes. Slow-phase gain was reduced and directional asymmetries were observed when optokinetic stimulation was restricted to the deprived eye.
Ascorbic acid increases the thyrotropin-releasing hormone content of hypothalamic cell cultures
Authors: Glombotski CC , Manaker S , Winokur A , Gibson TR
Published: March 2018

Thyrotropin-releasing hormone (TRH) is one of many COOH-terminal alpha- amidated neuropeptides. Recent work with the intermediate pituitary has indicated that ascorbate is a required cofactor for the COOH-terminal alpha-amidation of alpha-melanotropin. This is consistent with the ascorbate requirement of an enzyme found in pituitary and hypothalamus capable of converting peptides with a COOH-terminal glycine (-X-Gly) to alpha-amidated molecules (-H-NH2). Thus, it has been proposed that COOH- terminal glycine-extended TRH (TRH-Gly) may be the direct precursor to TRH. In the present study, primary hypothalamic cultures supplemented with ascorbate for 7 d contained two- to threefold more TRH immunoactivity (amide-specific) than cultures maintained without ascorbate. A dose-response experiment indicated that 20 microM ascorbate was capable of producing 50% of the maximum observable increase in culture TRH immunoactivity; this concentration is similar to the Km value for ascorbate uptake obtained in adrenal chromaffin and pituitary cells. A stereoisomer of ascorbate, D-isoascorbate, was also capable of producing an increase in TRH immunoactivity, but oxidized ascorbate was not. Recent studies have shown that the amidation enzyme from pituitary is capable of utilizing both L-ascorbate and D- isoascorbate but is incapable of utilizing oxidized ascorbate. The culture extracts were analyzed further by reversed-phase high- performance liquid chromatography; the increased TRH immunoactivity observed in extracts of cultures maintained in ascorbate comigrated with standard synthetic TRH.(ABSTRACT TRUNCATED AT 250 WORDS)
A protein associated with axon growth, GAP-43, is widely distributed and developmentally regulated in rat CNS
Authors: Jacobson RD , Virag I , Skene JH
Published: March 2018

Development or regeneration of axons in several systems is accompanied by 20-100-fold increases in the synthesis of an acidic, axonally transported membrane protein with an apparent molecular weight of 43- 50,000 (Benowitz and Lewis, 1983; Skene and Willard, 1981a, b), which we designate GAP-43. We have proposed that some step(s) in axon growth require production of GAP-43, and perhaps a small number of other “growth-associated proteins,” at rates much higher than those typical of mature neurons. This hypothesis predicts that virtually all neurons synthesize GAP-43 at elevated levels during normal CNS development. Here we show that a protein similar to GAP-43 from regenerating toad nerves is prominent among the newly synthesized (35S-methionine- labeled) and total (Coomassie blue-stained) proteins in neonatal rat cerebral cortex and cerebellum, suggesting that synthesis of GAP-43 is indeed a common feature of many developing neurons. Synthesis and accumulation of the protein decline an order of magnitude as animals mature. Antibodies raised against the rat cortex GAP-43 also recognize electrophoretically similar proteins from regenerating toad optic nerves and from developing hamster sensorimotor cortex, indicating that structural features of GAP-43 are conserved in evolution. Cell-free translation of polyadenylated RNA from neonatal and adult cortex suggests that developmental regulation of GAP-43 synthesis is mediated largely through changes in mRNA abundance. These observations together suggest that developmental regulation of GAP-43 gene expression may be common to most vertebrate CNS neurons. GAP-43 remains detectable at a low level in adult rat cortex, and it co-migrates on two-dimensional gels with B-50, a synaptic membrane protein which is a preferred substrate for protein kinase C in adult brains. Phosphorylation of the protein by endogenous kinase(s) in vitro is 4-7-fold greater in growth cone membranes than in mature synaptic membranes, which raises the possibility that local modification of the protein in axon terminals may be synergistic with regulation of GAP-43 synthesis in the cell body.
Normal olfactory discrimination learning set and facilitation of reversal learning after medial-temporal damage in rats: implications for an account of preserved learning abilities in amnesia
Authors: Eichenbaum H , Fagan A , Cohen NJ
Published: March 2018

Recent evidence of preserved skill learning in patients with “global” amnesia has led to the postulation of a qualitative distinction between functionally separate memory systems, one of which may remain preserved when the other is profoundly impaired. On one account, the separate memory systems support either the learning of declarative knowledge, i.e., facts and associations, or the learning of procedural knowledge, i.e., knowledge that permits the expression of skilled performance without reference to specific facts or associations. In an effort to develop a rodent model of amnesia that illustrates the same distinction between memory systems, rats were trained in a series of discrimination and reversal problems using olfaction, a sensory modality in which they rapidly learn new associations. Rats with bilateral fornix, amygdala, or combined fornix and amygdala damage learned successive two-odor discriminations as quickly as normal and sham-operated control subjects. Furthermore, all groups rapidly acquired the skills of discrimination as revealed in the development of a learning set. Subsequent presentation of a reversal of one discrimination elicited a marked dissociation among groups: Normal rats and rats with amygdala lesions required many more trials to acquire the reversal than to acquire a new discrimination problem, whereas rats with fornix lesions learned the reversal rather easily. A detailed analysis of response strategies suggested that normal rats and rats with amygdala lesions first extinguished the prior response tendencies and then abandoned the learning set skills and treated the reversal much as they did the initial discrimination problem.(ABSTRACT TRUNCATED AT 250 WORDS)
An in vitro model of proliferation and differentiation of the chick retina: coaggregates of retinal and pigment epithelial cells
Authors: Vollmer G , Layer PG
Published: March 2018

Pigment epithelial (PE) cells exert a pronounced organizing effect when added to embryonic day (E) 5–6 chick retinal cells in a reaggregation system such that after a period of 14–21 d of culture, the main layers of an intact E10-E14 retina are reconstructed (Vollmer et al., 1984). In the present study we investigated the time course of the formation of retina-like structures in retinal-pigment epithelial aggregates, in particular, the fate of the PE cells and their influence on processes of differentiation within the aggregates. PE cells first form a core in the center of the aggregates and migrate to the periphery at later stages. The PE core affects the organization of proliferation and differentiation, phenomena that were monitored using 3H-thymidine autoradiography and AChE histochemistry, respectively. A double- staining procedure combining both techniques on the same section is described. Soon after aggregation, a matrix zone and a zone of differentiated cells are formed. At later steps, proliferation becomes gradually restricted to a narrow band within the aggregates comparable to the in vivo situation. The spatiotemporal pattern of withdrawal from mitosis resembles that of the in vivo retina. Proliferation in aggregates is sustained over a longer period with PE, as compared with aggregates formed by retinal cells alone. AChE staining in aggregates in the presence of PE shows a layered appearance, while there is only crude sorting-out of labeled and unlabeled cells in aggregates composed of retinal cells only. The basis of PE cell action as well as the relevance of this in vitro system for understanding normal eye development are briefly discussed.
Branching of sensory and sympathetic neurites in vitro is inhibited by treatment with taxol
Authors: Letourneau PC , Shattuck TA , Ressler AH
Published: March 2018

Branching of elongating neurites in vitro occurs by the division of a growth cone into 2 or more daughter neurites. An important initial step is a broadening of the growth cone with establishment of a quiescent central growth cone margin. Within the spreading growth cone, microtubules and associated neuritic components diverge and become oriented toward the lateral protrusive margins of the leading edge (Letourneau, 1983). We have found that a low concentration of the microtubule-stabilizing agent taxol severely reduces the incidence of growth cone branching by cultured sensory and sympathetic neurons from chick embryos. In the presence of taxol, neurites are broader and have more microtubules than normally. Divergence of microtubules entering the growth cone from the proximal neurite is reduced in the presence of taxol, and quiescence of the central growth cone margin is less frequent. We propose that a critical step in branching is the separation and spreading of the neurite cytoskeleton by tensions generated at the lateral margins of the edge of the growth cone. Because taxol increases neurite size and microtubule content without increasing protrusive activity to the same extent, tensions produced in the motile leading edge are insufficient to spread the microtubules and associated neuritic materials into separate arrays for nascent branches.
Measurements of calcium transients in the soma, neurite, and growth cone of single cultured neurons
Authors: Bolsover SR , Spector I
Published: March 2018

Voltage-gated changes in cytosolic free calcium ion concentration were measured in single, differentiated cells of mouse neuroblastoma clone N1E-115 using the calcium-sensitive dye arsenazo III (AIII). In cells bathed in normal medium containing 10 mM calcium, the changes in AIII absorbance during a single action potential indicated an increase of 1.4 nM in cytosolic calcium. When 10 mM tetraethylammonium (TEA) was added to the bath, the action potential became prolonged and the change in cytosolic calcium increased to 3.9 nM. Under these conditions, repetitive stimulation at 0.5 Hz or faster caused a gradual decline in the amplitude and duration of the action potential and a gradual decline of the change in cytosolic calcium associated with each action potential. The amplitude of the prolonged after-hyperpolarization (AHP) that follows the action potential was found to reflect the magnitude of the change in cytosolic calcium. An action potential elicited in the cell soma caused an increase in cytosolic calcium in the soma, neurite, and growth cone regions of a single cell, indicating that the membrane of all three regions possesses voltage-gated calcium channels. Estimation of calcium flux per unit area of membrane suggests a distinct topographical organization of calcium channels. Calcium channel densities in the growth cone and cell soma regions are similar and significantly higher than that in the neurite.
Concanavalin A prevents acetylcholine receptor redistribution in Xenopus nerve-muscle cultures
Authors: Kidokoro Y , Brass B , Kuromi H
Published: March 2018

During neuromuscular junction formation ACh receptors accumulate at the nerve-contact region. It has been shown that this is at least partly due to lateral migration of existing receptors in the membrane (Anderson et al., 1977). Randomly diffusing ACh receptor molecules in the membrane may be trapped at the nerve-contact region to form a high receptor density area. If this were the major mechanism, cross-linking ACh receptors by tetravalent concanavalin A (Con A) should immobilize receptors and prevent nerve-induced receptor accumulation. We examined the effect of Con A on nerve-induced receptor accumulation and on the mobility of ACh receptors in cultured Xenopus muscle cells. ACh receptors were stained with tetramethyl rhodamine conjugated alpha- bungarotoxin. The cells were then treated briefly with Con A, and neural tube cells were added to these cultures. The mobility of ACh receptors was measured by the fluorescence photobleaching recovery method. The Con A treatment prevented rapid diffusion of ACh receptors as well as nerve-induced receptor accumulation. Functional synapse formation was not inhibited by this treatment. In contrast, divalent succinyl Con A did not affect the mobility of ACh receptors nor prevent nerve-induced ACh receptor accumulation. When the Con A concentration was varied, the blocking effect on the nerve-induced receptor accumulation changed in parallel with the mobile fraction of receptors. Newly inserted ACh receptors after the Con A treatment were found to be mobile and to accumulate at the nerve-contact region. In these cultures, new receptors accumulated around old, immobilized receptors in some areas along the nerve contact. This observation suggests that new receptors were inserted elsewhere and migrated to the nerve-contact region surrounding immobilized old ones. In addition to the accumulation of receptors, the nerve disperses preexisting receptor clusters prior to induction of high-density regions along the contact area, and, at this early stage, denervation disperses nerve-induced receptor clusters in Xenopus cultures (Kuromi and Kidokoro, 1984a, b). When cultures were treated with Con A, neither of these events occurred, suggesting that these are also diffusion-mediated.
Differential expression of mouse neural cell-adhesion molecule (N-CAM) mRNA species during brain development and in neural cell lines
Authors: Gennarini G , Hirsch MR , He HT , Hirn M , Finne J , Goridis C
Published: March 2018

The cell-adhesion molecules N-CAM (neural cell-adhesion molecule) are ligands in the formation of cell-cell bonds and have been shown to play important roles during neuro-ontogenesis. They exist in several molecular forms which differ at the protein and carbohydrate levels. The regulation of the expression of these different forms is an important issue that bears on such questions as to how adhesive interactions between cells are modulated during morphogenesis. In the present study we have used N-CAM cDNA clones to investigate the expression of the cognate mRNAs in the mouse and rat brain and in 2 neural cell lines. The results were compared with the levels of the different N-CAM proteins. We made the following observations. A complex set of 5 size classes of mRNAs--which show developmental, regional, and cell-type-dependent variations in their expression--hybridize to 1 of our cDNA probes. While embryonic brain contains N-CAM gene transcripts 7.4, 6.7, and 4.3 kilobases (kb) in length, 2 additional mRNAs of 5.2 and 2.9 kb appear postnatally. Transformed brain cells of an astrocytic character express predominantly mRNAs of 6.7, 4.3, and 2.9 kb and a neuroblastoma line those of 7.4, 6.7, 4.3, and 2.9 kb. There are important quantitative changes in the amount of N-CAM message expressed during brain development, with a peak around birth, suggesting that N- CAM synthesis is controlled at the transcriptional level. A comparison of N-CAM protein and mRNA levels reveals a striking correlation between the relative concentrations of the Mr 120,000 N-CAM protein (N-CAM120) and the 5.2 kb transcript.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of nerve growth factor on differentiation of muscle spindles following nerve lesion in neonatal rats
Authors: Sekiya S , Homma S , Miyata Y , Kuno M
Published: March 2018

Central synaptic function of Group Ia sensory fibers has been shown to be enhanced by daily applications of NGF in neonatal rats. In the periphery, Group Ia sensory fibers are known to trigger the differentiation of muscle spindles. In the present study we examined, in neonatal rats, whether daily NGF treatment affects the number or structure of spindles formed in muscle whose nerve has been crushed. The results show that 25–35 d after nerve crush, de novo supernumerary spindles were formed by treatment with NGF in the temporarily denervated muscle. The number of spindles in the corresponding muscle on the contralateral, intact side was not affected by NGF treatment. Following nerve crush alone, the mean number of spindles in the muscle was not significantly different from the normal value. It is suggested that treatment of neonatal rats with NGF may facilitate the outgrowth of excessive peripheral collaterals of regenerating Group Ia sensory fibers, which, in turn, contributes to the formation of de novo spindles as a result of interaction with myotubes.
Monoclonal antibodies to the dentate gyrus: immunocytochemical characterization and flow cytometric analysis of hippocampal neurons bearing a unique cell-surface antigen
Authors: Moskal JR , Schaffner AE
Published: March 2018

Monoclonal antibodies were generated using 5 d neonatal rat dentate gyrus as immunogen. One antibody of this panel, G6E3, recognized a cell- surface protein with an Mr = 43,000 that was found only in the nervous system. The antigen was expressed as early as embryonic day 13 in the rat in both the brain and spinal cord. In the adult rat the antigen was demonstrated immunohistochemically to be restricted to dentate gyrus granule, hippocampal pyramidal, and cerebellar Purkinje neurons. These results suggested that the antigen recognized by G6E3 may be developmentally regulated. Moreover, G6E3 did not appear to bind to mitotic cells, implying that the antigen was expressed after the terminal mitosis. The antibody also bound to hippocampal and cerebellar cells from mouse brain, including the reeler mutant, and rat hippocampal neurons in vitro. Double-labeling experiments performed on embryonic rat hippocampal cultures with G6E3 and antibodies to neuron- specific enolase (NSE) or anti-glutamic acid decarboxylase (GAD) revealed that only NSE-positive cells were immunoreactive for G6E3 and, while G6E3-positive cells were decorated with GAD-positive boutons, their cell bodies did not contain GAD. With the use of a fluorescence- activated cell sorter it was possible to analyze the immune reaction on embryonic and postnatal hippocampal cells and to sort G6E3-positive neurons for maintenance in vitro.
3H-batrachotoxinin-A benzoate binding to voltage-sensitive sodium channels: inhibition by the channel blockers tetrodotoxin and saxitoxin
Authors: Brown GB
Published: March 2018

The sodium channel blockers tetrodotoxin (TTX) and saxitoxin (STX) and the channel activator batrachotoxin (BTX) produce their effects by binding to separate and distinct sites on the channel protein. The fact that TTX- and STX-modified sodium channels are blocked to sodium flux has precluded drawing any direct conclusions regarding the effect of TTX/STX on BTX binding based on electrophysiological or 22Na flux measurements. Nevertheless, these sites have been presumed to be non- interacting. In this study, 3H-batrachotoxinin-A benzoate (BTX-B), a tritiated congener of BTX, has been used to provide a direct assessment of these binding interactions. Equilibrium specific binding of 3H-BTX-B to sodium channels in vesicular preparations of mouse brain in the presence of scorpion toxin was measured using a filtration assay procedure. At 25 degrees C both TTX and STX inhibit 3H-BTX-B binding in a concentration-dependent and noncompetitive manner. This inhibition is markedly temperature-dependent, being negligible at 37 degrees C and maximal at 18 degrees C, the lowest temperature investigated. Scatchard analysis of BTX-B binding isotherms at 25 degrees C in the presence and absence of 1 microM TTX revealed that inhibition is due to a 3-fold decrease in the affinity of BTX-B binding with no change in the number of binding sites (Bmax). The concentration dependence for TTX inhibition of both specific 3H-STX and 3H-BTX-B binding is identical, suggesting that inhibition of 3H-BTX-B binding is due to a direct effect of TTX/STX binding at their specific sodium channel site. The channel blockers did not alter the binding of scorpion toxin under these assay conditions, nor did BTX-B affect the binding of 3H- STX.(ABSTRACT TRUNCATED AT 250 WORDS)
Acute lesion of the intrafusal muscle of muscle spindles: ultrastructural and electrophysiological consequences
Authors: Quick DC
Published: March 2018

Experiments were performed to functionally separate the neural and muscular elements in muscle spindles. Cat muscle spindles were dissected free in vitro and were transected on both sides of the sensory nerve endings. This resulted in an acute lesion of the intrafusal muscle fibers but spared the sensory endings. Within 45 min, the intrafusal muscle fibers degenerated to the condition in which there were no myofilaments left in the sensory zone and the muscle fiber membrane had begun to disintegrate. During this degeneration period, and afterward, the sensory nerve fibers continued to fire action potentials. However, the postlesion discharge was usually more irregular than normal, and the mean rate of firing was often dramatically increased. In addition, multiplex frequencies of firing were often observed; that is, the interspike intervals were clustered around 2 or more modal values. Computer modeling of 2 action potential initiators competing for access to the same output line suggests that the multiplexing results from at least one of the competitors having a fraction of its spikes aborted. Overall, the results indicate that the nerve endings have an intrinsic capability to function as sensory receptors in the absence of a muscle substrate.
Binocular impulse blockade prevents the formation of ocular dominance columns in cat visual cortex
Authors: Stryker MP , Harris WA
Published: March 2018

Ocular dominance columns in the cat's visual cortex appear to develop out of an initially overlapping projection by a progressive segregation of the geniculocortical afferents serving the 2 eyes (reviewed in LeVay and Stryker, 1979). To determine whether electrical activity in the visual afferent pathway is involved in this normal, developmental rearrangement of synaptic connections, we blocked the discharge of retinal ganglion cells in both eyes by making repeated intravitreal injections of tetrodotoxin (TTX) during the period in which geniculocortical afferent segregation would normally be taking place. Control experiments for the side effects of the injection procedure, the systemic effects of TTX, and the effects of visual deprivation were carried out, and a series of normal animals of appropriate ages was also studied. We then examined the effects of retinal blockade and the various control procedures on the formation of ocular dominance columns using an anatomical assay, the autoradiographic labeling of geniculocortical afferent terminals in layer IV of the visual cortex by the transneuronal transport of tritiated proline injected into 1 eye, and a physiological assay, the ocular dominance of single cortical cells recorded extracellularly. After retinal TTX blockade, layer IV was labeled uniformly without periodic fluctuation in grain density, and nearly all cortical cells were driven well through both eyes. These assays thus indicated that retinal blockade completely blocked the formation of ocular dominance columns, unlike any of the control procedures, suggesting that the spontaneous maintained discharge of retinal ganglion cells may have an important role in the normal development of binocular connections in the visual cortex.
Morphology and electrophysiological properties of reticularis thalami neurons in cat: in vivo study of a thalamic pacemaker
Authors: Mulle C , Madariaga A , Deschenes M
Published: March 2018

Reticularis thalami neurons (RE neurons) were identified morphologically, and their electrophysiological properties were studied in cat under barbiturate anesthesia. Intracellular HRP injections showed that RE neurons possessed very long dendrites bearing numerous filopodia-like appendages and that their axons were directed toward main thalamic nuclei. As a rule, small axonal branches were also emitted within the RE nucleus itself. At rest, the membrane potential of RE neurons displayed 2 types of oscillations: a slow 0.1–0.2 Hz oscillation and fast 7–12 Hz oscillations occurring on the positive phase of the former. Episodes of spindle (7–12 Hz) waves lasted for 2–3 sec and were characterized by rhythmic depolarizations and burst discharges. Intracellular injections of QX314 and current pulse analyses revealed the presence in RE cells of 2 distinct inward currents: a persistent current that promoted tonic firing and a low- threshold current deinactivated by hyperpolarization that generated burst discharges. The low-threshold current deinactivated with large somatic hyperpolarizations (up to 30 mV) and produced depolarizing responses that lasted for about 70 msec. In addition, low-threshold responses appeared rhythmically at intervals of about 150 msec after recovery of the membrane potential from hyperpolarization. Because of their duration, voltage dependence, and persistence after intracellular injections of QX314, it is suggested that these responses resulted from activation of a low-threshold Ca2+ current at the dendritic level. In QX314-injected cells, selective components of spontaneous oscillations were abolished, among them the positive phase of the slow oscillation and late depolarizing humps that followed burst discharges within spindle sequences. However, the rhythmic occurrence of spindle episodes at 0.1–0.2 Hz was never affected by DC currents or by QX314 or Cl- injections, suggesting that oscillations within a particular RE neuron partly reflected the oscillatory behavior of a network of cells. On the basis of these electrophysiological results and the known morphological and neurochemical features, a new hypothesis is proposed to account for the rhythmicity of RE neurons.
Nerve growth factor promotes survival of septal cholinergic neurons after fimbrial transections
Authors: Hefti F
Published: March 2018

Several findings obtained in recent years suggest that NGF, aside from its well-established function as a neurotrophic factor for peripheral sympathetic and sensory neurons, also has trophic influence on the cholinergic neurons of the basal forebrain. The present study assessed whether NGF was able to affect survival of central cholinergic neurons after axonal transections in adult rats. The septo-hippocampal pathway was transected unilaterally by cutting the fimbria, and animals were implanted with a cannula through which NGF or control solutions were injected intraventricularly over 4 weeks. The lesions reduced the number of large cell bodies, as visualized by Nissl staining in the medial septal nucleus and in the vertical limb of the diagonal band of Broca. Furthermore, in the same nuclei, they reduced the number of cell bodies positively stained for AChE after pretreatment with diisopropylfluorophosphate (a method known to result in reliable identification of cholinergic neurons in the septal area). On lesioned sides, the number of cholinergic cells in medial septal nucleus and the vertical limb of the diagonal band was reduced by 50 +/- 4%, as compared to the number on contralateral sides. On lesioned sides of animals chronically treated with NGF, the number of AChE-positive cells in these areas was reduced only by 12 +/- 6%, as compared to control levels. These findings suggest that fimbrial transections resulted in retrograde degeneration of cholinergic septo-hippocampal neurons and that NGF treatment strongly attenuated this lesion-induced degeneration.(ABSTRACT TRUNCATED AT 250 WORDS)
Ontogeny of substance P receptor binding sites in rat brain
Authors: Quirion R , Dam TV
Published: March 2018

The ontogeny of substance P (SP) receptor binding sites in rat brain has been studied using both membrane binding assays and in vitro receptor autoradiography. The density of SP binding sites is maximal 1 d before birth and decreases thereafter to reach adult values 14 d after birth. During the early postnatal period, the distribution of SP binding sites undergoes major modifications. For example, very high densities of SP binding sites are present in most brain stem nuclei from 1 to 14 d after birth, while it is not the case in adults. In the striatum, SP receptors are distributed in a “patchy” manner early after birth, while it is much more homogeneous in the adult. This demonstrates that SP receptors undergo major redistributions during postnatal development. The very high density of SP binding sites present in the brain at its early stages of development may indicate that SP could be an important factor involved in the early organization of the CNS.
Deafferentation elicits increased dopamine-sensitive adenylate cyclase and receptor binding in the olfactory tubercle
Authors: Lingham RB , Gottesfeld Z
Published: March 2018

Removal of a major non-catecholaminergic output from the olfactory bulb elicits sprouting of dopaminergic axons in the olfactory tubercle. The functional consequences of this increased dopaminergic innervation are presently not known. This study examined the question of whether lesion- induced sprouting of dopaminergic axons is associated with changes in dopamine-sensitive adenylate cyclase and dopamine receptor density in the partially denervated olfactory tubercle. The results indicate that dopamine- and NaF-stimulated adenylate cyclase activity increased as early as 7 d, while forskolin-sensitive activity increased at 3 d and persisted up to 20 d after lesioning; higher levels of GTP- and NaF- stimulated enzyme activity were found in detergent extracts of olfactory tubercle membranes from 20 d lesioned rats; higher levels of 3H-forskolin binding were found in membranes from 14 and 20 d lesioned rats; and there was an increase in dopamine receptor density, but not affinity, in olfactory tubercle membranes from lesioned rats. The data indicate that lesion-induced dopaminergic sprouting in the olfactory tubercle is temporally coordinated with the increased formation of dopamine receptors, both D1 and D2, the stimulatory guanine nucleotide regulatory protein (Ns) and the catalytic subunit (C) of adenylate cyclase in the postsynaptic membrane.
In vitro release and electrophysiological effects in situ of homocysteic acid, an endogenous N-methyl-(D)-aspartic acid agonist, in the mammalian striatum
Authors: Do KQ , Herrling PL , Streit P , Turski WA , Cuenod M
Published: March 2018

A potassium-induced, calcium-dependent release of endogenous homocysteic acid (HCA) from rat striatal slices was demonstrated. A precolumn derivatization high-performance liquid chromatography method was developed that allowed quantitative determination of sulfur- containing amino acids at the picomole level. Intracellular recordings from cat caudate neurons during simultaneous microiontophoretic application of drugs and electrical stimulation of the corticocaudate pathway showed that (L)-HCA evoked a depolarization pattern similar to that induced by N-methyl-(D)-aspartic acid (NMDA), and both these depolarizations could be selectively inhibited by a specific NMDA antagonist, (D)-2-amino-7-phosphonoheptanoic acid [(D)-AP-7]. A selective antagonism of (L)-HCA-induced depolarizations by (D)-AP-7 was confirmed in quantitative experiments with the frog hemisected spinal cord in vitro. Small quantities of iontophoretically applied (L)-HCA, but not of quisqualate, potentiated cortically evoked EPSPs in cat caudate neurons. These observations suggest that (L)-HCA might be a candidate as an NMDA-receptor-preferring endogenous transmitter in the caudate nucleus. One possible function for such transmitter systems could be the enhancement of EPSPs.
Morphological transformation of synaptic terminals of a phasic motoneuron by long-term tonic stimulation
Authors: Lnenicka GA , Atwood HL , Marin L
Published: March 2018

In vivo stimulation of a relatively “silent” phasic crayfish motoneuron changes the ultrastructure of its synaptic terminals to a more tonic phenotype. The closer muscle of the crayfish claw is supplied by only 2 excitatory motoneurons, one of which is phasic and the other tonic. The ultrastructures of conditioned phasic, unconditioned phasic, and tonic motor terminals were compared. The terminals of the tonic motor axon were larger in cross-sectional area, had larger mitochondria, greater synaptic contact area, and were more varicose than unconditioned phasic terminals. Following long-term tonic stimulation of the phasic axon, its terminals became more varicose, mitochondrial cross-sectional area more than doubled, and synapses and mitochondria came into closer proximity, although mean terminal cross-sectional area did not change. Thus, the conditioned phasic terminals became more similar to those of the tonic motor axon. These changes in ultrastructure correlate with, and may be causally linked to, previously reported changes in neuromuscular synaptic physiology produced by in vivo tonic stimulation of this motoneuron. We conclude that the ongoing level of impulse activity can affect the ultrastructural differentiation of synaptic terminals and synapses of the phasic motoneuron.
Blends of rostral and caudal scratch reflex motor patterns elicited by simultaneous stimulation of two sites in the spinal turtle
Authors: Stein PS , Camp AW , Robertson GA , Mortin LI
Published: March 2018

Simultaneous tactile stimulation of 2 sites on the body surface of a spinal turtle elicits complex blends of the scratch forms and motor patterns associated with each site. Our previous work has utilized 1- site stimulation to elicit distinct forms of the scratch reflex in the spinal turtle (Mortin et al., 1985; Robertson et al., 1985). Using this paradigm, stimulation of a site on the shell bridge anterior to the hindlimb elicits a rostral scratch reflex in which the dorsum of the foot rubs against the stimulated site; stimulation of a site near the tail elicits a caudal scratch reflex in which the heel or side of the foot rubs against the stimulated site (Mortin et al., 1985). During each scratch cycle, the monoarticular knee extensor muscle is active when the limb rubs against the stimulated site, and there is rhythmic alternation between hip protractor and hip retractor muscle activity (Robertson et al., 1985). In a rostral scratch, the monoarticular knee extensor muscle is active during the latter portion of hip protractor muscle activity; in a caudal scratch, the monoarticular knee extensor muscle is active near the end of hip retractor muscle activity. Pure- form motor patterns that are similar to those recorded from these muscles during movement can be recorded from the corresponding nerves in a spinal turtle immobilized with a neuromuscular blocking agent (Robertson et al., 1985). In this paper, we describe blend responses to simultaneous stimulation of 2 sites, one in the rostral scratch and the other in the caudal scratch receptive field. During these blends, the responding hindlimb rubs against both stimulated sites in one continuous movement sequence.(ABSTRACT TRUNCATED AT 250 WORDS)