bluuebunny/crossref_metadata_2025 huggingface dataset:
RB and Cdc2 expression in brain: correlations with 3H-thymidine incorporation and neurogenesis
Authors: Okano HJ , Pfaff DW , Gibbs RB
Published: March 2018

Expression of the cell cycle regulatory proteins RB and p34cdc2 was examined in the adult rat brain, with special emphasis on proliferation and neuronal differentiation in the hippocampal formation and olfactory bulb. RB-like immunoreactivity (RB-IR) was detected throughout the brain, with particularly intense staining observed in hippocampal pyramidal cells, pyriform cortex, and cerebellar Purkinje cells. Intense RB-IR and cdc2-IR were also detected in proliferating neuronal precursor cells in the subgranular region of the dentate gyrus and in the subependymal region extending from the anterior lateral ventricle into the olfactory bulb. Many of these cells developed into neurons as assessed by the expression of neuron-specific enolase (NSE) and, in the hippocampal formation, the expression of Fos-IR following pentylenetetrazol-induced seizure activity. A good correlation was observed between the number of proliferating cells expressing intense nuclear RB-IR staining and the number of thymidine-labeled cells that had differentiated into functional hippocampal neurons. A substantial decrease in RB-IR during differentiation was also observed and occurred prior to the expression of NSE. The possibility that the loss of RB may be necessary for neuronal differentiation to proceed is discussed.
Role of glucocorticoids in the cholinergic degeneration in rat hippocampus induced by ethylcholine aziridinium (AF64A)
Authors: Hortnagl H , Berger ML , Havelec L , Hornykiewicz O
Published: March 2018

Glucocorticoids potentiate hippocampal damage induced by various noxious insults in vivo and in vitro and are implicated in age-related loss of neurons in the hippocampus of various species. The cholinergic innervation of the hippocampus appears to be especially prone to the endangering effect of glucocorticoids, since corticosterone, like acute stress or ACTH, induces a rapid activation of the cholinergic septo- hippocampal pathway. We now report the influence of glucocorticoids on the degeneration of this pathway induced by the cholinergic neurotoxin ethylcholine aziridinium (AF64A). The toxic effect of a submaximal dose of AF64A on cholinergic neurons was evaluated in rats during exposure to glucocorticoids or vehicle as well as in adrenalectomized or sham- operated rats. Daily treatment with either corticosterone or dexamethasone, starting 7 d before the bilateral intracerebroventricular injection of AF64A (1 nmol/ventricle), significantly increased the AF64A-induced loss of ChAT activity in the whole hippocampus, whereas bilateral adrenalectomy 7 d prior to AF64A- injection attenuated the effect of AF64A. Short-term exposure to corticosterone starting 24 hr before AF64A was as effective as the 7 d pretreatment. Dexamethasone exacerbated the AF64A-induced cholinergic lesion in the hippocampal subregions CA1, CA3, and dentate gyrus, and adrenalectomy protected all subregions against the action of AF64A. Along the longitudinal axis of the hippocampus a comparable influence was seen in the dorsal and ventral parts. The subregional pattern in the response to glucocorticoid suggests the involvement of mineralocorticoid type I receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
Structure-function relationships in rat brainstem subnucleus interpolaris. X. Mechanisms underlying enlarged spared whisker projections after infraorbital nerve injury at birth
Authors: Jacquin MF , Zahm DS , Henderson TA , Golden JP , Johnson EM , Renehan WE , Klein BG
Published: March 2018

Prior studies indicate that the central projections of noninfraorbital vibrissae occupy greater than normal transverse areas in the rat trigeminal brainstem complex after infraorbital nerve section at birth. Here, we assessed the development of this phenomenon and possible underlying mechanisms. Cytochrome oxidase patches representing spared supraorbital (SO) or posteroorbital (PO) whiskers in the trigeminal subnucleus interpolaris (SpVi) were not reliably larger than those on the control side 24 hr after the infraorbital lesion. By 72 hr, SO and PO patches were 91% and 28% larger than those on the control side. Reliable increases were also observed on postnatal day 5 (PND5), PND7, and PND10 for the SO (59%, 65%, 66%) and PO (23%, 44%, 51%) patches. To test the hypothesis that central reorganization reflects the maintenance of peripheral supernumerary axons, myelinated and unmyelinated axons in SO vibrissa follicles were counted at PND0, PND7, PND17, and PND60. A corollary hypothesis, that peripheral regeneration errors result in both SO and surviving infraorbital axons, contributing to central SO patches, was tested with retrograde double-labeling methods. Both hypotheses were rejected. Thus, enlargement of SO patches is not due to either the maintenance of an immature peripheral innervation pattern, or regeneration of infraorbital axons into SO follicles. To determine if the enlargement of SO and PO patches produced by infraorbital nerve section is due to an activity-dependent competitive disadvantage imposed upon infraorbital afferents, TTX or bupivicaine was applied to the intact infraorbital nerve over the first 5–9 postnatal days. Brainstem maps developed normally and SO and PO patch areas were unaffected. Thus, impulse activity-based mechanisms do not appear to contribute to injury-induced patch enlargement. To test the hypothesis that patch enlargement is due to central collateral reorganization, intra-axonal recording and staining methods were applied to control and spared-whisker primary afferents in adult rats. Total bouton or collateral numbers did not differ in SpVi; however, arbor areas were reliably larger in experimental (14,879 +/- 350 microns 2) versus control (5527 +/- 1811 microns 2) fibers.(ABSTRACT TRUNCATED AT 400 WORDS)
Selective distribution of kainate receptor subunit immunoreactivity in monkey neocortex revealed by a monoclonal antibody that recognizes glutamate receptor subunits GluR5/6/7
Authors: Huntley GW , Rogers SW , Moran T , Janssen W , Archin N , Vickers JC , Cauley K , Heinemann SF , Morrison JH
Published: March 2018

A monoclonal antibody (4F5) was generated against a portion of the putative extracellular domain of glutamate receptor subunit GluR5. Western blot analyses and immunocytochemistry of transfected human embryonic kidney 293 cells confirmed that monoclonal antibody 4F5 was specific for GluR5, -6, and -7 (the three identified members of the kainate receptor subunit class), but did not recognize GluR1, -2, or -3 (the AMPA/kainate receptor subunit class). The antibody was subsequently used to examine immunocytochemically the regional, laminar, and cellular distribution of GluR5/6/7 receptor subunits at the light and electron microscopic levels in monkey neocortex. Receptor subunit immunoreactivity was present throughout all cortical areas examined, but exhibited marked cellular, laminar, and regional specificity. Typically, pyramidal cell somata and apical dendrites were well stained. Electron microscopy revealed an extensive cytoplasmic localization of GluR5/6/7 immunoprecipitate, with intense staining of many postsynaptic densities, all of which were associated with asymmetric synapses located on dendritic shafts or dendritic spines. There was no evidence of stained glial cells or presynaptic axon terminals. In most areas, labeled cells and dendrites were concentrated in layers II, III, and V while layers I, IV, and VI typically possessed the fewest and/or least intensely stained elements. A consistent feature in many areas was groups of clustered layer V pyramidal cells and bundles of ascending apical dendrites. Regionally, motor areas and higher-order association areas of the frontal, parietal, and occipital lobes were more densely stained than primary sensory areas (somatic sensory and visual cortex), which was confirmed quantitatively. These data indicate a high degree of selectivity in the distribution of kainate receptors composed of GluR5/6/7 subunits, and suggest that functional specificity and diversity in the ubiquitous excitatory amino acid-utilizing axonal systems in neocortex are achieved in part by the differential association of particular glutamate receptor subunits with specific cortical circuits. In addition, the regional, laminar, and morphological characteristics of GluR5/6/7-immunoreactive neurons bear a strong similarity to those of the neocortical neurons with heightened vulnerability in certain neurodegenerative disorders.
Lectin identification of olfactory receptor neuron subclasses with segregated central projections
Authors: Riddle DR , Wong LD , Oakley B
Published: March 2018

Our previous studies have demonstrated that the primary olfactory projection in rainbow trout is organized nontopographically; the pattern of termination of olfactory axons in the olfactory bulb is unrelated to the distribution of their cell bodies in the olfactory mucosa. In the present research we have further characterized the organization of this projection by examining the lectin-binding properties of olfactory receptor neurons. The results indicate that in trout, as in mammals, populations of olfactory receptor neurons differ significantly from one another in their carbohydrate “signatures.” We have identified subsets of olfactory receptor neurons, specified by unique lectin-binding properties, that are widely distributed and intermingled with the other receptor neurons in the olfactory mucosa and nerve, but that segregate as they enter the olfactory bulb and project to restricted regions of the glomerular layer. This pattern of terminations is bilaterally symmetrical, is remarkably consistent across individuals, and reappears when the primary olfactory projection is reconstituted following transection of the olfactory nerve. As revealed by the carbohydrates on subpopulations of receptor neurons, there is substantial order in the nontopographic projection of olfactory receptor neurons to the olfactory bulb. The functional significance of this organization and the means by which it develops and is maintained remain under investigation.
Peptide growth factors protect against ischemia in culture by preventing nitric oxide toxicity
Authors: Maiese K , Boniece I , DeMeo D , Wagner JA
Published: March 2018

Reduction or elimination of nitric oxide (NO) production in cortical neurons by NO synthase (NOS) inhibitors during glutamate toxicity in vitro or during focal cerebral ischemia in vivo can prevent neuronal cell death. In contrast, growth factors can prevent neuronal degeneration induced by treatment with glutamate or potassium cyanide. We have determined whether NO mediates hippocampal cell death during anoxia in vitro and whether the peptide growth factors basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) can prevent hippocampal neuronal death during anoxia or NO exposure. Both bFGF and EGF increased hippocampal neuronal survival from about 35% in anoxic cultures to about 65% in treated cultures during an 8 hr period of anoxia. Inhibition of NOS by NG-monomethyl-L-arginine, a competitive inhibitor of NOS, rescued 65–70% of the neurons that would normally die during an 8 hr anoxic incubation, and this effect was reversed by L- arginine, a precursor for NO. Thus, hippocampal neuronal death following anoxia is, at least in part, mediated by NO. NO, generated by either nitroprusside or 3-morpholino-sydnonimine, was toxic to hippocampal neurons. Pretreatment of cultures with either bFGF (10 ng/ml) or EGF (10 ng/ml) prior to NO exposure increased survival from approximately 40% in untreated cultures to 80% in treated cultures, yet the effect of combining bFGF and EGF was not greater than treatment with either of the growth factors alone. Knowledge that the growth factors bFGF and EGF are neuroprotective against NO toxicity provides insights into the mechanisms of ischemic neuronal death that may direct future therapeutic modalities for cerebrovascular disease and neurodegenerative disorders.
Differential immunohistochemical localization of inositol 1,4,5- trisphosphate- and ryanodine-sensitive Ca2+ release channels in rat brain
Authors: Sharp AH , McPherson PS , Dawson TM , Aoki C , Campbell KP , Snyder SH
Published: March 2018

Ca2+ release from inositol 1,4,5-trisphosphate (IP3)-sensitive and ryanodine-sensitive intracellular Ca2+ stores is mediated by distinct proteins identified as IP3 receptors (IP3R) and ryanodine receptors (RyR), respectively. We have compared the immunohistochemical localizations of IP3R and RyR in the brain at the light and electron microscopic levels and have also evaluated the distribution of the major brain intracellular Ca(2+)-pumping ATPase. IP3R and RyR occur in overlapping populations of neurons in widespread areas of the brain, but labeling is distinct in a number of areas. For example, IP3R is enriched in cerebellar Purkinje cells and hippocampal CA1 pyramidal cells, while RyR is present at relatively low levels in these cells. RyR is most enriched in the dentate gyrus and CA3/4 areas of the hippocampus, where IP3R levels are low. In the cortex, IP3R is found in pyramidal cell bodies and proximal dendrites, whereas RyR is located predominantly in long, thin apical dendrites of pyramidal cells. In deep cerebellar nuclei, RyR is located in cell bodies that appear devoid of IP3R, whereas IP3R is enriched in terminals surrounding cell bodies. Electron microscopy in the hippocampus reveals RyR in axons, dendritic spines, and dendritic shafts near dendritic spines while IP3R is primarily identified in dendritic shafts and cell bodies. These results suggest that the IP3- and ryanodine-sensitive Ca2+ pools have largely distinct roles in controlling intracellular Ca2+ levels, though in some sites they may interact to varying degrees.
Facilitation and depression at different branches of the same motor axon: evidence for presynaptic differences in release
Authors: Katz PS , Kirk MD , Govind CK
Published: March 2018

This study provides evidence that a neuron can exhibit differences in activity-dependent transmitter release at two synaptic sites due to variations in the properties of its presynaptic terminals. Two muscles in the stomatogastric system of the lobster Homarus americanus are innervated by a single motor neuron but respond differently to that motor neuron's input, resulting in two different movements evoked by one motor neuron. During continued motor neuron stimulation, the gm8 muscle contracts slowly and maintains contraction, while the gm9 muscle contracts rapidly and then relaxes. These different muscle responses can be accounted for, in large part, by the properties of the respective neuromuscular synapses: the excitatory junctional potentials recorded in gm8 are initially small but summate and facilitate with repeated stimulation, while those in gm9 are initially large but depress with repeated stimulation. Presynaptic differences in neurotransmitter release contribute strongly to the divergent responses; reduction of the excitatory junction potential amplitude by partial postsynaptic receptor blockade or by desensitization does not change the amount of depression at gm9. However, reduction of neurotransmitter release with low-Ca2+, high-Mg2+ saline removes gm9 synaptic depression and reveals that both neuromuscular junctions exhibit frequency-dependent homosynaptic facilitation. Postsynaptic differences in muscle input resistance and muscle composition may enhance the effects of the divergent release properties, but are not responsible for the activity-dependent changes. Ultrastructural features of the nerve terminals on the two muscles are consistent with the differential output of the terminals; the synapses on gm9 are larger and have more presynaptic dense bars than their counterparts on gm8. These data suggest that the basis for the differences in transmitter release between the two muscles may be a higher density of release sites in the gm9 synapses that leads to a higher output of neurotransmitter, rapid depletion of transmitter stores, and synaptic depression.
Membrane potential changes in sphincter motoneurons during micturition in the decerebrate cat
Authors: Fedirchuk B , Shefchyk SJ
Published: March 2018

Intracellular recordings from external urethral sphincter (EUS) and external anal sphincter (EAS) motoneurons were obtained during micturition in the decerebrate cat. The neural circuitry mediating micturition was activated by distension of the bladder or by electrical stimulation of the pontine micturition center (PMC). During micturition, the membrane potential of EUS motoneurons hyperpolarized 3– 9 mV, during which time the motoneuron somatic membrane conductance increased. The membrane hyperpolarization could be reversed with passive diffusion or active ejection of chloride from the intracellular microelectrode into the motoneuron. In contrast, the membrane potential of EAS motoneurons either depolarized slightly or showed no change during micturition. We have shown that the neural circuitry mediating micturition can influence the EUS and EAS independently. In addition, stimulation of the PMC provides a valuable tool for identifying spinal neurons mediating the postsynaptic inhibition of EUS motoneurons during micturition.
Reduction of intramuscular nerve branching and synaptogenesis is correlated with decreased motoneuron survival
Authors: Tang J , Landmesser L
Published: March 2018

Blockade of neuromuscular activity during the period of naturally occurring cell death increases intramuscular nerve branching, synaptogenesis, and survival of embryonic chicken motoneurons. These results suggested that the enhanced motoneuron survival observed might result not from increased production of a trophic factor by the target, as often suggested, but rather from the enhanced ability of motoneurons to take up this factor via additional branches and/or synapses. Since removal of polysialic acid (PSA) by PSA-specific endoneuraminidase (endo N) during the period of nerve ingrowth and motoneuron cell death had been shown to reduce intramuscular nerve branching by altering adhesive interactions between axons and myotubes, we wished to determine, first, if this resulted in a reduction of synapse formation, and second, if this was correlated with decreased motoneuron survival. When PSA was removed from embryonic day 6 (E6) to E9 by injecting endo N into the limb, the number of synapses in the posterior iliotibialis muscle was greatly reduced both at E6.5, the onset of the cell death period, and at E7.5-E8, the middle of the cell death period. Total motoneuron counts at both E7.5-E8 and E10 (close to the end of cell death period) were significantly decreased compared to controls. These results indicate that a treatment that reduces intramuscular nerve branching and synapse formation also affects motoneuron survival. Furthermore, since removal of PSA in ovo via endo N altered neither the spontaneous embryonic motility nor the activation pattern of motoneurons or muscles, these experiments avoid the complication of activity blockade that may alter motoneuron survival by affecting events other than, or in addition to, intramuscular nerve branching.
Intraneuronal compartments of the amyloid precursor protein
Authors: Ferreira A , Caceres A , Kosik KS
Published: March 2018

The amyloid precursor protein (APP) is the parent molecule from which beta-amyloid protein is cleaved and deposits as amyloid fibrils in the senile plaques of Alzheimer's disease. Its primary structure resembles a receptor; however, no ligand has been identified. In growing hippocampal neurons APP is localized to growth cones. APP immunoreactivity was highly enriched in the axons of mature cultured neurons, where it appears as a specialization of the axonal membrane. Its anterograde translocation occurs via a kinesin-based motor. Following cytosolic acidification, APP colocalizes with late endosomes that get redistributed from the neuronal cell body to the processes. APP colocalizes in cultured hippocampal neurons to clathrin- immunoreactive clusters of vesicular-like structures. The finding lends additional credence to the possibility that APP could function as a receptor.
Depolarization maintains neurites and priming of PC12 cells after nerve growth factor withdrawal
Authors: Teng KK , Greene LA
Published: March 2018

In contrast to its actions on certain neural populations, membrane depolarization by elevated K+ promotes neither the survival nor the differentiation of PC12 cells. We therefore employed this model system to examine directly the actions of elevated K+ on neurites. Here we report that elevated K+ prevents the degeneration of neurites that occurs when NGF is withdrawn from PC12 cell cultures. This effect is inhibited by the L-type Ca2+ channel blockers verapamil and nitrendipine. Although depolarization preserves preexisting neurites, unlike NGF, it does not promote neurite elongation. In addition to neurite stabilization, elevated K+ also maintains NGF-deprived cells in a “primed” state in which they can rapidly regenerate neurites when re- treated with NGF. Elevated K+ alone has no priming effect, nor is it neuritogenic on either naive or NGF-pretreated cells. To probe the molecular basis for these actions of depolarization, we examined several cytoskeletal proteins whose phosphorylations (beta-tubulin, MAP 1.2/1B, and 64, 72 and 80 kDa chartins) or levels (MAP 1.2/1B and peripherin) are regulated by NGF in parallel with neurite outgrowth. Elevated K+ alone does not mimic these effects of NGF. In all cases, NGF withdrawal leads to the return of these proteins to levels characteristic of naive cells; in contrast, with the exception of the 80 kDa chartins, depolarization of NGF-deprived cultures maintained these proteins at or near their NGF-stimulated states. Similar observations were obtained with the NILE/L1 glycoprotein. These findings suggest that elevated K+ preserves priming and preexisting neurites by maintaining NGF-induced changes in cell composition. Our experiments invoke the possibility that elevation of intraneuronal Ca2+ may lead to selective stabilization of preexisting axons or dendrites in the intact nervous system, especially under circumstances in which the supply of neurotrophic factors is absent or limiting.
Identification and transport of full-length amyloid precursor proteins in rat peripheral nervous system
Authors: Sisodia SS , Koo EH , Hoffman PN , Perry G , Price DL
Published: March 2018

Amyloid deposits are a characteristic feature of the senile plaques identified in the brains of aged primates, individuals with Down's syndrome, and cases of Alzheimer's disease. The beta-amyloid protein (A beta), the principal component of amyloid, is a 4 kDa peptide derived from larger amyloid precursor protein(s) (APP). Four mRNAs, generated by alternative splicing of pre-mRNA derived from a single gene, encode A beta-containing membrane glycoproteins termed APP-695, -714, -751, and -770; the latter two isoforms contain a domain homologous to Kunitz protease inhibitors (KPI). The present study uses in vitro and in vivo strategies to examine the expression of APP in neurons of the dorsal root ganglia and the nature of APP transported in sciatic nerves of rats. Using quantitative in situ hybridization and semiquantitative PCR analysis, we document that mRNAs encoding APP-695 are expressed preferentially over transcripts that encode KPI-containing isoforms in rat sensory ganglia. Furthermore, we provide compelling evidence that APP-695 is the predominant isoform synthesized in sensory neurons of the rat PNS and that full-length APP-695 and, to a lesser extent, APP- 751/770 are rapidly transported anterogradely in axons.
Spatially restricted expression of Dlx-1, Dlx-2 (Tes-1), Gbx-2, and Wnt- 3 in the embryonic day 12.5 mouse forebrain defines potential transverse and longitudinal segmental boundaries
Authors: Bulfone A , Puelles L , Porteus MH , Frohman MA , Martin GR , Rubenstein JL
Published: March 2018

The expression patterns of four genes that are potential regulators of development were examined in the CNS of the embryonic day 12.5 mouse embryo. Three of the genes, Dlx-1, Dlx-2 (Tes-1), and Gbx-2, encode homeodomain-containing proteins, and one gene, Wnt-3, encodes a putative secreted differentiation factor. These genes are expressed in spatially restricted transverse and longitudinal domains in the embryonic neural tube, and are also differentially expressed within the wall of the neural tube. Dlx-1 and Dlx-2 are expressed in two separate regions of the forebrain in an identical pattern. The Gbx-2 gene is expressed in four domains, two of which share sharp boundaries with the domains of the Dlx genes. One boundary is in the basal telecephalon between deep and superficial strata of the medial ganglionic eminence; the other boundary is in the diencephalon at the zona limitans intrathalamica. The Wnt-3 gene is expressed in a dorsal longitudinal zone extending from the hindbrain into the diencephalon, where its expression terminates at the zona limitans intrathalamica. Reciprocal patterns of expression are found within the dorsal thalamus for the Gbx- 2 and Wnt-3 genes. These findings are consistent with neuromeric theories of forebrain development, and based upon them we suggest a model for forebrain segmentation.
Purkinje cell survival is differentially regulated by metabotropic and ionotropic excitatory amino acid receptors
Authors: Mount HT , Dreyfus CF , Black IB
Published: March 2018

We previously reported that trophic factors and neurotransmitters in concert regulate survival of cultured cerebellar Purkinje cells. In particular, excitatory amino acid (EAA) transmitters and NGF increased survival, whereas neither alone was effective. In the present studies, we sought to identify molecular mechanisms through which EAAs participate in the survival-promoting interaction. Initially, we characterized the potential role of ionotropic EAA receptors by exposing cultures to the antagonists MK-801, D-2-amino-5- phosphonovaleric acid, and 6,7-dinitroquinoxalinedione. Each increased cell number, suggesting that endogenous ionotropic activity decreased survival. To determine whether metabotropic EAA receptor stimulation modulates survival, the metabotropic agonist ACPD ([1S,3R]-1- aminocyclopentane-1,3-dicarboxylic acid; 1 microM) was tested. ACPD alone had no effect on survival. However, simultaneous exposure to ACPD and NGF significantly increased Purkinje number. Moreover, this increase in survival was blocked by L-AP3 [L(+)-2-amino-3- phosphonopropionic acid; 1 microM], a putative antagonist of certain metabotropic responses. L-AP3 also reduced cell number in the absence of exogenous EAA. Thus, endogenous metabotropic stimulation is normally necessary for survival. In sum, these studies reveal a novel mechanism whereby an excitatory neurotransmitter shapes neural development by simultaneous trophic and regressive actions that are, respectively, mediated by metabotropic and ionotropic EAA receptors.
Output architecture of the primate putamen
Authors: Flaherty AW , Graybiel AM
Published: March 2018

The basal ganglia act through direct and indirect striatopallidal output pathways that have different effects on cortical activity. This division has been proposed to underlie the fundamental distinction between hyperkinetic and hypokinetic movement disorders such as Parkinson's disease and Huntington's disease. Evidence to date does not favor a relationship between this dual organization and the division of the striatum into striosome and matrix compartments. However, the possibility has been raised that the division of striatopallidal output paths reflects a compartmentalization of the matrix itself into clusters of different striatopallidal projection neurons. We directly tested this hypothesis in squirrel monkeys by comparing the distributions of striatal output neurons retrogradely labeled from the two pallidal segments. Striatopallidal neurons labeled by small injections confined to either the external pallidum (GPe) or the internal pallidum (GPi) formed small clusters (“matrisomes”) in the matrix compartment of the putamen. However, contrary to previous predictions, labeled matrisomes projecting to GPe were not systematically separated from those projecting to GPi. They could overlap extensively, and within individual matrisomes GPe-projecting neurons and GPi-projecting neurons were extensively intermixed. Double- retrograde labeling analysis in single sections demonstrated that only 2.1 +/- 2.7% of labeled striatal neurons were doubly labeled from both GPe and GPi--a number not significantly different from zero. GPe- projecting and GPi-projecting neurons in the putamen also differed sharply in their expression of enkephalin-like immunoreactivity: 71.3 +/- 7.6% of the neurons labeled by GPe injections were enkephalin positive, in contrast to 10.0 +/- 3.6% of the neurons labeled by GPi injections. These results suggest that in the primate, populations of striatopallidal output neurons are grouped in clusters in the matrix, but that individual neurons in any given cluster project either to GPe or to GPi. Matrisomal clustering may thus coordinate signals sent into the direct and indirect pathways of the basal ganglia from distributed populations of projection neurons in the striatum.
The slow (< 1 Hz) oscillation in reticular thalamic and thalamocortical neurons: scenario of sleep rhythm generation in interacting thalamic and neocortical networks
Authors: Steriade M , Contreras D , Curro Dossi R , Nunez A
Published: March 2018

As most afferent axons to the thalamus originate in the cerebral cortex, we assumed that the slow (< 1 Hz) cortical oscillation described in the two companion articles is reflected in reticular (RE) thalamic and thalamocortical cells. We hypothesized that the cortically generated slow rhythm would appear in the thalamus in conjunction with delta and spindle oscillations arising from intrinsic and network properties of thalamic neurons. Intracellular recordings have been obtained in anesthetized cats from RE (n = 51) and cortically projecting (n = 240) thalamic neurons. RE cells were physiologically identified by cortically evoked high-frequency spike bursts and depolarizing spindle oscillations. Thalamocortical cells were recognized by backfiring from appropriate neocortical areas, spindle- related cyclic IPSPs, and hyperpolarization-activated delta oscillation consisting of rhythmic low-threshold spikes (LTSs) alternating with afterhyperpolarizing potentials (AHPs). The slow rhythm (0.3–0.5 Hz) was recorded in 65% of RE neurons. In approximately 90% of oscillating cells, the rhythm consisted of prolonged depolarizations giving rise to trains of single action potentials. DC hyperpolarization increased the synaptic noise and, in a few cells, suppressed the long-lasting depolarizing phase of the slow rhythm, without blocking the fast EPSPs. In approximately 10% of oscillating neurons, the hyperpolarizing phase of the oscillation was much more pronounced, thus suggesting that the slow rhythm was produced by inhibitory sculpturing of the background firing. The slow oscillation was associated with faster rhythms (4–8 Hz) in the same RE neuron. The slow rhythm of RE neurons was closely related to EEG wave complexes recurring with the same frequency, and its strong dependency upon a synchronized state of cortical EEG was observed during shifts in EEG patterns at different levels of anesthesia. In 44% of thalamocortical cells the slow rhythm of depolarizing sequences was apparent and it could coexist with delta or spindle oscillations in the same neuron. The occurrence of the slowly recurring depolarizing envelopes was delayed by the hyperpolarizing spindle sequences or by the LTS-AHP sequences of delta oscillation. The hyperpolarization-activated delta potentials that tended to dampen after a few cycles were grouped in sequences recurring with the slow rhythm. We finally propose a unified scenario of the genesis of the three major sleep rhythms: slow, delta, and spindle oscillations.
Phosphoinositide second messenger system is enriched in striosomes: immunohistochemical demonstration of inositol 1,4,5-trisphosphate receptors and phospholipase C beta and gamma in primate basal ganglia
Authors: Fotuhi M , Dawson TM , Sharp AH , Martin LJ , Graybiel AM , Snyder SH
Published: March 2018

The neurochemical organization of the basal ganglia has been studied extensively with respect to neurotransmitters, neuropeptides, and their receptors. The chemoarchitecture of the striatum has been found particularly striking, because it distinguishes many substances by their relative distributions within the striosome and matrix compartments of the striatum. Very little is yet known about the differential distribution of second messenger systems in the basal ganglia, however, and no information is available about whether the distribution of second messenger systems is related to the prominent neurochemical compartmentalization of the striatum. We have examined the distribution of the phosphoinositide second messenger system in the primate basal ganglia and substantia nigra, as detected with polyclonal antisera against the inositol 1,4,5-trisphosphate receptor (IP3R), and monoclonal antisera against phospholipase C beta (PLC beta) and phospholipase C gamma (PLC gamma). In the striatum, immunostaining for each of the three proteins was present predominantly in medium-sized neuronal perikarya and in the neuropil. Circumscribed zones of enhanced IP3R, PLC beta, and PLC gamma immunoreactivity appeared in a background of generally weaker staining, and these zones corresponded to striosomes as identified by calbinidin D28k and substance P immunostaining in adjacent sections. Thus, the richest representation of the phosphoinositide system in the primate striatum appears to be in striosomes. In the substantia nigra pars compacta, neurons and neuropil were immunopositive, but in the substantia nigra pars reticulata and in each segment of the globus pallidus, immunostaining was mainly confined to the neuropil. Perikaryal PCL gamma immunoreactivity in the absence of detectable PLC beta or IP3R immunolabeling was found in the magnocellular neurons embedded in the medullary layer between the putamen and the globus pallidus. These observations demonstrate that the phosphoinositide second messenger system is selectively enhanced in neuronal subsystems of the basal ganglia, including striosomes, and suggest that signaling by phosphoinositide pathways elicits discrete effects on input-output processing by the basal ganglia.
Development of segment specificity in identified lineages of the grasshopper CNS
Authors: Thompson KJ , Siegler MV
Published: March 2018

The purpose of this study was to determine the factors underlying differences in population size and composition between segmentally homologous neuronal lineages. The segmental median neuroblasts (MNBs) of grasshoppers are identified stem cells that each produce a midline group of neurons. We traced the embryonic development of the group in two disparate segments, counting MNB progeny and profiles of dying cells in fixed and stained preparations of staged embryos. In the metathoracic segment (T3), about 95 MNB progeny survive embryonic development, whereas in the next posterior segment, the first abdominal (A1), only about 60 survive. In T3, the MNB arises at 29% of embryogenesis and dies at 78%, whereas in A1 the MNB arises at 30% and dies at 73%. In T3, the number of MNB progeny initially increases at a steady rate, 10 cells being added per 5% of embryogenesis. Between 70% and 78% growth tapers off; although the T3 MNB continues to divide, cells die at the same time, specifically removing last-born progeny. By contrast, in A1 the MNB progeny increase in two phases, one from 30% to 45% and the other from 60% to 73%, again at the rate of 10 cells per 5%. Between the two phases, the number of A1 progeny is stable. The A1 MNB continues to divide, but cells die at the same time, specifically removing earlier-born progeny. The episodes of cell death in A1 and T3 coincide with embryonic molts, and thus may be hormonally triggered. Cell death is greater in A1 than T3, accounting for most of the difference in population size. The difference in MNB longevity makes a lesser contribution. The present data, together with corollary anatomical data (Thompson and Siegler, 1991), support the hypothesis that progeny fated to become certain neuronal types are selectively removed from the two MNB lineages: intersegmental interneurons from T3 and efferent neurons and local interneurons from A1.
The buccalin-related neuropeptides: isolation and characterization of an Aplysia cDNA clone encoding a family of peptide cotransmitters
Authors: Miller MW , Beushausen S , Cropper EC , Eisinger K , Stamm S , Vilim FS , Vitek A , Zajc A , Kupfermann I , Brosius J
Published: March 2018

The buccalin-related peptides, buccalin A and buccalin B, are members of a family of cotransmitters that modulate neuromuscular transmission in Aplysia. In this study, a third buccalin-related peptide, buccalin C, was purified from neuronal elements in the accessory radula closer, a muscle involved in the animal's feeding behavior. Oligonucleotide probes based upon the amino acid sequence of buccalin C were used to isolate cDNA clones that encode a buccalin precursor polypeptide. The buccalin precursor contains 19 distinct buccalin-related peptides, several of which are present in multiple copies. The buccalin gene appears to be present in a single copy, with one allele containing a small insert. Expression of this gene occurs in a tissue-specific manner and mRNA transcripts are abundant within neurons in the Aplysia CNS. This large family of neuropeptides may exert extraordinarily complex modulatory actions at synapses where they serve as cotransmitters.
The myomodulin-related neuropeptides: characterization of a gene encoding a family of peptide cotransmitters in Aplysia
Authors: Miller MW , Beushausen S , Vitek A , Stamm S , Kupfermann I , Brosius J , Weiss KR
Published: March 2018

The myomodulin-related peptides comprise a family of cotransmitters that modulate neuromuscular signaling in the feeding system of Aplysia. In this study, cDNA clones encoding a myomodulin precursor polypeptide were isolated and characterized. This precursor contains seven different myomodulin-related peptides, one of which, myomodulin A, is present in 10 contiguous copies. The sequence of a myomodulin genomic clone indicates that all of these myomodulin-related peptides are encoded on a single exon. The myomodulin gene is expressed in a tissue- specific manner and myomodulin mRNA is localized to specific neurons in the Aplysia CNS. The presence of multiple related neuropeptides can greatly increase the range and precision of signaling at synapses where they act as modulator cotransmitters.
Modulation of hippocampal acetylcholine release: a potent central action of interleukin-2
Authors: Hanisch UK , Seto D , Quirion R
Published: March 2018

The potential of the T-cell growth factor interleukin-2 (IL-2) to modulate the release of ACh from rat hippocampus was studied in vitro, as a means to investigate the possible functional significance of this cytokine in the CNS. Hippocampal slices were superfused with Krebs' buffer medium, and endogenous ACh released into the superfusate was measured using a radioenzymatic assay. Recombinant human IL-2 present during a stimulation with 25 mM KCl altered, in a concentration- dependent manner, the evoked transmitter release. At a concentration of 15 U/ml (< or = 1 nM), IL-2 inhibited ACh release by more than 50% of the control level (evoked ACh release from the untreated contralateral hemispheres). Inhibition was observed within 20 min of tissue exposure to IL-2 and lasted for up to 1 hr. The inhibitory effect of IL-2 was reversible since transient tissue exposure to IL-2 did not affect subsequent evoked ACh release. IL-2 at this concentration also significantly decreased evoked ACh in frontal cortical slices, but was ineffective in the parietal cortex and striatum, revealing that IL-2 selectively modulates the release of ACh from certain, but not all, cholinergic nerve terminals in the CNS. At very low concentrations (1.5 mU/ml, < or = 0.1 pM), IL-2 transiently increased hippocampal evoked ACh release, resulting in a biphasic dose-response profile with no significant effect observed at 0.015 mU/ml (< or = 1 fM). Other cytokines (IL-1 alpha, IL-3, IL-5, IL-6, interferon alpha), tested in hippocampal slice incubations, failed to modulate ACh release.(ABSTRACT TRUNCATED AT 250 WORDS)
Vacuole dynamics in growth cones: correlated EM and video observations
Authors: Dailey ME , Bridgman PC
Published: March 2018

The neuronal growth cone is a major site of surface membrane dynamics associated with uptake and release of materials, motility, and axon extension. Although intracellular membrane organelles are thought to mediate surface membrane addition and retrieval at the growth cone, membrane events are fleeting and therefore difficult to study directly. In an effort to capture transient interactions between intracellular membrane organelles and the plasmalemma at the growth cone, embryonic rat sympathetic neuron cultures were prepared for whole-mount electron microscopy (EM) by rapid freezing and freeze substitution. We identified a set of vacuole-like organelles (> or = 150 nm in diameter) that appeared to interact directly with the plasmalemma. In stereo-pair EM images the bounding membrane of some of these vacuoles had an orifice at sites where the organelle was adjoining the plasmalemma, suggesting that the organelle and surface membranes were confluent. Since this population of organelles could be labeled with cationized ferritin or HRP when added to living cultures just prior to freezing or chemical fixation, they were probably derived from the plasmalemma. Combined light microscopy and EM of individual growth cones showed that these same vacuoles had a conspicuous reverse shadowcast appearance in differential interference contrast images. Thus, we used real-time video microscopy to follow these organelles in living growth cones. Many of these vacuoles spontaneously appeared, remained visible for several minutes, and then disappeared. Reverse shadowcast vacuoles were formed at various sites throughout the growth cone, including surface membrane ruffles at the leading edge [P (peripheral)-domain] as well as quiescent and retracting regions at the growth cone base [C (central)- domain]. Vacuoles in the P-domain moved centripetally and rarely grew in size. In contrast, those in the C-domain exhibited Brownian-like movements and sometimes appeared to increase in size, raising the possibility that new membrane may be added to these organelles. Vacuoles within both the P- and C-domains shrank before rapidly disappearing, but rarely vesiculated, suggesting that they had fused with the plasmalemma. The results indicate that vacuoles are a highly dynamic population of organelles that directly communicate with the plasma membrane at the growth cone; they provide a major route of surface membrane uptake and may also play a role in membrane recycling.
Degradation of two AChR populations at rat neuromuscular junctions: regulation in vivo by electrical stimulation
Authors: Andreose JS , Xu R , Lomo T , Salpeter MM , Fumagalli G
Published: March 2018

The effect of electrical stimulation on the stability of junctional ACh receptors (AChR) on soleus muscles of Wistar rats was compared to that of denervation and reinnervation. Denervation causes the degradation rate of the slowly degrading AChRs (Rs) at the neuromuscular junction to accelerate and be replaced by rapidly degrading AChRs (Rr), while reinnervation restabilizes the accelerated Rs. Electrical stimulation initiated at the time of denervation prevented the acceleration of the Rs. It could not, however, reverse the effect of denervation if initiated after the AChRs became destabilized, nor could it slow the degradation rate of the Rr. We conclude that electrical stimulation of denervated muscle downregulates the expression of the Rr and prevents the destabilization of Rs.
Dopaminergic modulation of dye coupling between neurons in the core and shell regions of the nucleus accumbens
Authors: O'Donnell P , Grace AA
Published: March 2018

The presence of dye coupling and electrotonic coupling within the nucleus accumbens was examined using intracellular recording and staining in rat brain slices. In 24% of the cells examined, injection of single accumbens neurons with the dye Lucifer yellow resulted in the complete labeling of more than one cell. To examine whether this coupling is regulated by dopamine (DA), the extent of dye coupling was assessed in the presence of dopaminergic agonists and antagonists. In the core region of the accumbens, D1 receptor stimulation induced a decrease in the incidence of dye coupling; this effect could be blocked by the D1 antagonists SCH 23,390 and SCH 39,166, by the D2 antagonist sulpiride, or by depletion of DA by reserpine and alpha-methyl-p- tyrosine coadministration, but not by the atypical antipsychotic drug clozapine. In contrast, in the posterior part of the shell region, D2 receptor stimulation increased the incidence of coupling independent of the state of D1 receptor activation. Fast spikelets resembling coupling potentials were found to occur only in neurons that also showed dye coupling, and could be attenuated in core neurons by D1 receptor stimulation. These findings suggest that DA, in addition to its actions on the membrane of single neurons, may also affect neuronal integration on a network level by regulating the transfer of information between adjacent neurons within the nucleus accumbens.
Combined oxygen and glucose deprivation in cortical cell culture: calcium-dependent and calcium-independent mechanisms of neuronal injury
Authors: Goldberg MP , Choi DW
Published: March 2018

Murine neocortical cell cultures were transiently deprived of both oxygen and glucose, producing widespread neuronal swelling in less than 60 min, followed by neuronal degeneration over the ensuing several hours, despite return to normal medium. Cultured glia (> 95% astrocytes) were irreversibly injured only by oxygen-glucose deprivation exposures exceeding 4–6 hr. Replacing either Na+ or Cl- with impermeant ions blocked acute neuronal swelling but did not prevent delayed neuronal degeneration. While neuronal swelling and death were increased by removing Ca2+ from the exposure medium, combined removal of extracellular Ca2+ together with Na+ or Cl- substitution blocked both acute and delayed injury. If acute swelling was limited by a hyperosmolar medium, then neuronal loss depended on extracellular [Ca2+]. Oxygen-glucose deprivation was associated with a large increase in extracellular glutamate concentration. Both early swelling and later neuronal degeneration were blocked by addition of NMDA receptor antagonists to the exposure medium but not by the AMPA/kainate receptor antagonist 6-cyano-7-dinitroquinoxaline-2,3-dione (CNQX), dihydropyridines nifedipine or nimodipine, or TTX. Oxygen- glucose deprivation induced substantial neuronal uptake of tracer 45Ca2+ from the exposure medium that was reduced by NMDA receptor antagonists and closely paralleled the degree of subsequent neuronal loss. These observations suggest the presence of two distinct components of hypoxic injury, each involving NMDA receptor activation and each capable of leading to neuronal death. Acute swelling is mediated by influx of Na+, Cl-, and water, and is enhanced by removal of extracellular Ca2+. Delayed neuronal degeneration depends on the presence of extracellular Ca2+ and correlates closely with cellular uptake of 45Ca2+.