bluuebunny/crossref_metadata_2025 huggingface dataset:
Suppression of Neuronal Hyperexcitability and Associated Delayed Neuronal Death by Adenoviral Expression of GABACReceptors
Authors: Cheng Qing , Kulli John C. , Yang Jay
Published: April 2018

The excessive neuronal excitation underlying several clinically important diseases is often treated with GABA allosteric modulators in an attempt to enhance inhibition. An alternative strategy would be to enhance directly the sensitivity of postsynaptic neurons to GABA. The GABACreceptor, normally found only in the retina, is more sensitive to GABA and demonstrates little desensitization compared with the GABAAreceptor. We constructed an adenovirus vector that expressed cDNA for both the GABACreceptor ρ1subunit and a green fluorescent protein (GFP) reporter and used it to transduce cultured hippocampal neurons. Transduced neurons were identified by fluorescence, double immunocytochemistry proved colocalization of the ρ1protein and the reporter, Western blot verified the expected molecular masses, and electrophysiological and pharmacological properties confirmed the presence of functional GABACreceptors. ρ1-GFP transduction resulted in an increased density of GABAAreceptors as well as expression of novel GABACreceptors. This effect was not reproduced by addition of TTX or Mg2+to the culture medium to reduce action potentials or synaptic activity. In a model of neuronal hyperexcitability induced by chronic blockade of glutamate receptors, expression of GABACreceptors abolished the hyperactivity and the consequent delayed neuronal death. Adenovirus-mediated neuronal GABACreceptor engineering, via its dual mechanism of inhibition, may offer a way of inhibiting only those hyperexcitable neurons responsible for clinical problems, avoiding the generalized nervous system depression associated with pharmacological therapy.
Differential Expression of the Small-Conductance, Calcium-Activated Potassium Channel SK3 Is Critical for Pacemaker Control in Dopaminergic Midbrain Neurons
Authors: Wolfart Jakob , Neuhoff Henrike , Franz Oliver , Roeper Jochen
Published: April 2018

The physiological activity of dopaminergic midbrain (DA) neurons is important for movement, cognition, and reward. Altered activity of DA neurons is a key finding in schizophrenia, but the cellular mechanisms have not been identified. Recently, KCNN3, a gene that encodes a member (SK3) of the small-conductance, calcium-activated potassium (SK) channels, has been proposed as a candidate gene for schizophrenia. However, the functional role of SK3 channels in DA neurons is unclear. We combined patch-clamp recordings with single-cell RT-PCR and confocal immunohistochemistry in mouse midbrain slices to study the function of molecularly defined SK channels in DA neurons. Biophysical and pharmacological analysis, single-cell mRNA, and protein expression profiling strongly suggest that SK3 channels mediate the calcium-dependent afterhyperpolarization in DA neurons. Perforated patch recordings of DA neurons in the substantia nigra (SN) demonstrated that SK3 channels dynamically control the frequency of spontaneous firing. In addition, SK3 channel activity was essential to maintain the high precision of the intrinsic pacemaker of DA SN neurons. In contrast, in the ventral tegmental area, DA neurons displayed significantly smaller SK currents and lower SK3 protein expression. In these DA neurons, SK3 channels were not involved in pacemaker control. Accordingly, they discharged in a more irregular manner compared with DA SN neurons. Thus, our study shows that differential SK3 channel expression is a critical molecular mechanism in DA neurons to control neuronal activity. This provides a cellular framework to understand the functional consequences of altered SK3 expression, a candidate disease mechanism for schizophrenia.
Complex Trait Analysis of the Hippocampus: Mapping and Biometric Analysis of Two Novel Gene Loci with Specific Effects on Hippocampal Structure in Mice
Authors: Lu Lu , Airey David C. , Williams Robert W.
Published: April 2018

Notable differences in hippocampal structure are associated with intriguing differences in development and behavioral capabilities. We explored genetic and environmental factors that modulate hippocampal size, structure, and cell number using sets of C57BL/6J (B6) and DBA/2J (D2) mice; their F1 and F2 intercrosses (n= 180); and 35 lines of BXD recombinant inbred (RI) strains. Hippocampal weights of the parental strains differ by 20%. Estimates of granule cell number also differ by ∼20%. Hippocampal weights of RI strains range from 21 to 31 mg, and those of individual F2 mice range from 23 to 36 mg (bilateral weights). Volume and granule cell number are well correlated (r= 0.7–0.8). Significant variation is associated with differences in age and sex. The hippocampus increases in weight by 0.24 mg per month, and those of males are 0.55 mg heavier (bilateral) than those of females.

Heritability of variation is ∼50%, and half of this genetic variation is generated by two quantitative trait loci that map to chromosome 1 (Hipp1a: genome-widep< 0.005, between 65 and 100 cM) and to chromosome 5 (Hipp5a,p< 0.05, between 15 and 40 cM). These are among the first gene loci known to produce normal variation in forebrain structure.Hipp1aandHipp5aindividually modulate hippocampal weight by 1.0–2.0 mg, an effect size greater than that generated by age or sex. TheHippgene loci modulate neuron number in the dentate gyrus, collectively shifting the population up or down by as much as 200,000 cells. Candidate genes for theHipploci includeRxrgandFgfr3.
Adaptive Locomotor Plasticity in Chronic Spinal Cats after Ankle Extensors Neurectomy
Authors: Bouyer Laurent J. G. , Whelan Patrick J. , Pearson Keir G. , Rossignol Serge
Published: April 2018

After lateral gastrocnemius–soleus (LGS) nerve section in intact cats, a rapid locomotor compensation involving synergistic muscles occurs and is accompanied by spinal reflex changes. Only some of these changes are maintained after acute spinalization, indicating the involvement of descending pathways in functional recovery. Here, we address whether the development of these adaptive changes is dependent on descending pathways. The left LGS nerve was cut in three chronic spinal cats. Combined kinematics and electromyographic (EMG) recordings were obtained before and for 8 d after the neurectomy. An increased yield at the ankle was present early after neurectomy and, as in nonspinal cats, was gradually reduced within 8 d. Compensation involved transient changes in step cycle structure and a longer term increase in postcontact medial gastrocnemius (MG) EMG activity. Precontact MG EMG only increased in one of three cats. In a terminal experiment, the influence of group I afferents from MG and LGS on stance duration was measured in two cats. LGS effectiveness at increasing stance duration was largely decreased in both cats. MG effectiveness was only slightly changed: increased in one cat and decreased in another. In cat 3, the plantaris nerve was cut after LGS recovery. The recovery time courses from both neurectomies were similar (p> 0.8), suggesting that this spinal compensation is likely a generalizable adaptive strategy. From a functional perspective, the spinal cord therefore must be considered capable of adaptive locomotor plasticity after motor nerve lesions. This finding is of prime importance to the understanding of functional plasticity after spinal injury.
Spatiotemporal Maps of Brain Activity Underlying Word Generation and Their Modification during Repetition Priming
Authors: Dhond Rupali P. , Buckner Randy L. , Dale Anders M. , Marinkovic Ksenija , Halgren Eric
Published: April 2018

Spatiotemporal maps of brain activity based on magnetoencephalography were used to observe sequential stages in language processing and their modification during repetition priming. Subjects performed word-stem completion and produced either novel or repeated (primed) words across trials. Activation passes from primary visual cortex (activated at ∼100 msec after word presentation), to left anteroventral occipital (∼180 msec), to cortex in and near Wernicke's (∼210 msec) and then Broca's (∼370 msec) areas. In addition, a posteroventral temporal area is activated simultaneously with posterosuperior temporal cortex. This area shows an early (∼200–245 msec) increase in activation to repeated word stems. In contrast, prefrontal and anterior temporal regions showed activity reductions to repeated word stems late (∼365–500 msec) in processing. These results tend to support classical models of language and suggest that an effect of direct item repetition is to allow word-form processing to increase its contribution to task performance while concurrently allowing reductions in time-consuming frontal temporal processing.
5-HT2AReceptors Stimulate ACTH, Corticosterone, Oxytocin, Renin, and Prolactin Release and Activate Hypothalamic CRF and Oxytocin-Expressing Cells
Authors: Van de Kar Louis D. , Javed Adil , Zhang Yahong , Serres Florence , Raap Danı́ K. , Gray Thackery S.
Published: April 2018

The 5-HT2A/2Cagonist (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl (DOI) stimulates hypothalamic neurons to increase the secretion of several hormones. This study addressed two questions: 1) are the neuroendocrine effects of DOI mediated via activation of 5-HT2Areceptors; and 2) which neurons are activated by 5-HT2Areceptors. The 5-HT2Aantagonist (+)-α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidinemethanol (MDL 100,907; 0.001, 0.01, or 0.1 mg/kg, s.c.) was administered before rats were challenged with DOI (2.5 mg/kg, i.p.). MDL 100,907 produced a dose-dependent inhibition (ED50≅ 0.001 mg/kg) of the effect of DOI on plasma levels of ACTH, corticosterone, oxytocin, prolactin, and renin without altering basal hormone levels. Complete blockade of the effect of DOI was achieved for all hormones at MDL 100,907 doses of 0.01–0.1 mg/kg. In a parallel experiment, DOI was injected 2 hr before killing to determine its effects on the expression of Fos, the product of the immediate early gene c-fos. DOI induced an increase in Fos immunoreactivity in corticotropin-releasing factor (CRF) and in oxytocin-expressing neurons but not in vasopressin-containing neurons in the hypothalamic paraventricular nucleus or CRF cells in the amygdala. Pretreatment with MDL 100,907 (0.1 mg/kg, s.c.) blocked the DOI-induced increase in Fos expression in all regions including the hypothalamus, amygdala (central and corticomedial), bed nucleus of the stria terminalis, and prefrontal cortical regions. The combined neuroanatomical and pharmacological observations suggest that the neuroendocrine responses to DOI are mediated by activation of neurons in the hypothalamic paraventricular nucleus and associated circuitry. Furthermore, selective activation of 5-HT2Areceptors mediates the hormonal and Fos-inducing effects of DOI.
Layer-Specific Intracolumnar and Transcolumnar Functional Connectivity of Layer V Pyramidal Cells in Rat Barrel Cortex
Authors: Schubert Dirk , Staiger Jochen F. , Cho Nichole , Kötter Rolf , Zilles Karl , Luhmann Heiko J.
Published: April 2018

Layer V pyramidal cells in rat barrel cortex are considered to play an important role in intracolumnar and transcolumnar signal processing. However, the precise circuitry mediating this processing is still incompletely understood. Here we obtained detailed maps of excitatory and inhibitory synaptic inputs onto the two major layer V pyramidal cell subtypes, intrinsically burst spiking (IB) and regular spiking (RS) cells, using a combination of caged glutamate photolysis, whole-cell patch-clamp recording, and three-dimensional reconstruction of biocytin-labeled cells. To excite presynaptic neurons with laminar specificity, the release of caged glutamate was calibrated and restricted to small areas of 50 × 50 μm in all cortical layers and in at least two neighboring barrel-related columns. IB cells received intracolumnar excitatory input from all layers, with the largest EPSP amplitudes originating from neurons in layers IV and VI. Prominent transcolumnar excitatory inputs were provided by presynaptic neurons also located in layers IV, V, and VI of neighboring columns. Inhibitory inputs were rare. In contrast, RS cells received distinct intracolumnar inhibitory inputs, especially from layers II/III and V. Intracolumnar excitatory inputs to RS cells were prominent from layers II–V, but relatively weak from layer VI. Conspicuous transcolumnar excitatory inputs could be evoked solely in layers IV and V. Our results show that layer V pyramidal cells are synaptically driven by presynaptic neurons located in every layer of the barrel cortex. RS cells seem to be preferentially involved in intracolumnar signal processing, whereas IB cells effectively integrate excitatory inputs across several columns.
Layer-Specific Input to Distinct Cell Types in Layer 6 of Monkey Primary Visual Cortex
Authors: Briggs Farran , Callaway Edward M.
Published: April 2018

Layer 6 of monkey V1 contains a physiologically and anatomically diverse population of excitatory pyramidal neurons. Distinctive arborization patterns of axons and dendrites within the functionally specialized cortical layers define eight types of layer 6 pyramidal neurons and suggest unique information processing roles for each cell type. To address how input sources contribute to cellular function, we examined the laminar sources of functional excitatory input onto individual layer 6 pyramidal neurons using scanning laser photostimulation. We find that excitatory input sources correlate with cell type. Class I neurons with axonal arbors selectively targeting magnocellular (M) recipient layer 4Cα receive input from M-dominated layer 4B, whereas class I neurons whose axonal arbors target parvocellular (P) recipient layer 4Cβ receive input from P-dominated layer 2/3. Surprisingly, these neuronal types do not differ significantly in the inputs they receive directly from layers 4Cα or 4Cβ. Class II cells, which lack dense axonal arbors within layer 4C, receive excitatory input from layers targeted by their local axons. Specifically, type IIA cells project axons to and receive input from the deep but not superficial layers. Type IIB neurons project to and receive input from the deepest and most superficial, but not middle layers. Type IIC neurons arborize throughout the cortical layers and tend to receive inputs from all cortical layers. These observations have implications for the functional roles of different layer 6 cell types in visual information processing.
Reorganization of Motor and Somatosensory Cortex in Upper Extremity Amputees with Phantom Limb Pain
Authors: Karl Anke , Birbaumer Niels , Lutzenberger Werner , Cohen Leonardo G. , Flor Herta
Published: April 2018

Phantom limb pain (PLP) in amputees is associated with reorganizational changes in the somatosensory system. To investigate the relationship between somatosensory and motor reorganization and phantom limb pain, we used focal transcranial magnetic stimulation (TMS) of the motor cortex and neuroelectric source imaging of the somatosensory cortex (SI) in patients with and without phantom limb pain. For transcranial magnetic stimulation, recordings were made bilaterally from the biceps brachii, zygomaticus, and depressor labii inferioris muscles. Neuroelectric source imaging of the EEG was obtained after somatosensory stimulation of the skin overlying face and hand. Patients with phantom limb pain had larger motor-evoked potentials from the biceps brachii, and the map of outputs was larger for muscles on the amputated side compared with the intact side. The optimal scalp positions for stimulation of the zygomaticus and depressor labii inferioris muscles were displaced significantly more medially (toward the missing hand representation) in patients with phantom limb pain only. Neuroelectric source imaging revealed a similar medial displacement of the dipole center for face stimulation in patients with phantom limb pain. There was a high correlation between the magnitude of the shift of the cortical representation of the mouth into the hand area in motor and somatosensory cortex and phantom limb pain. These results show enhanced plasticity in both the motor and somatosensory domains in amputees with phantom limb pain.
Bidirectional Dopamine Modulation of GABAergic Inhibition in Prefrontal Cortical Pyramidal Neurons
Authors: Seamans Jeremy K. , Gorelova Natalia , Durstewitz Daniel , Yang Charles R.
Published: April 2018

Dopamine regulates the activity of neural networks in the prefrontal cortex that process working memory information, but its precise biophysical actions are poorly understood. The present study characterized the effects of dopamine on GABAergic inputs to prefrontal pyramidal neurons using whole-cell patch-clamp recordingsin vitro. In most pyramidal cells, dopamine had a temporally biphasic effect on evoked IPSCs, producing an initial abrupt decrease in amplitude followed by a delayed increase in IPSC amplitude. Using receptor subtype-specific agonists and antagonists, we found that the initial abrupt reduction was D2 receptor-mediated, whereas the late, slower developing enhancement was D1 receptor-mediated. Linearly combining the effects of the two agonists could reproduce the biphasic dopamine effect. Because D1 agonists enhanced spontaneous (sIPSCs) but did not affect miniature (mIPSCs) IPSCs, it appears that D1 agonists caused larger evoked IPSCs by increasing the intrinsic excitability of interneurons and their axons. In contrast, D2 agonists had no effects on sIPSCs but did produce a significant reduction in mIPSCs, suggestive of a decrease in GABA release probability. In addition, D2 agonists reduced the postsynaptic response to a GABAAagonist. D1 and D2 receptors therefore regulated GABAergic activity in opposite manners and through different mechanisms in prefrontal cortex (PFC) pyramidal cells. This bidirectional modulation could have important implications for the computational properties of active PFC networks.
Coding Specificity in Cortical Microcircuits: A Multiple-Electrode Analysis of Primate Prefrontal Cortex
Authors: Constantinidis Christos , Franowicz Matthew N. , Goldman-Rakic Patricia S.
Published: April 2018

Neurons with directional specificities are active in the prefrontal cortex (PFC) during tasks that require spatial working memory. Although the coordination of neuronal activity in PFC is thought to be maintained by a network of recurrent connections, direct physiological evidence regarding such networks is sparse. To gain insight into the functional organization of the working memory systemin vivo, we recorded simultaneously from multiple neurons spaced 0.2–1 mm apart in monkeys performing an oculomotor delayed response task. We used cross-correlation analysis and characterized the effective connectivity between neurons in relation to their spatial and temporal response properties. The majority of narrow (<5 msec) cross-correlation peaks indicated common input and were most often observed between pairs of neurons within 0.3 mm of each other. Neurons recorded at these distances represented the full range of spatial locations, suggesting that the entire visual hemifield is represented in modules of corresponding dimensions. Nearby neurons could be activated in any epoch of the behavioral task (stimulus presentation, delay, response). The incidence and strength of cross-correlation, however, was highest among cells sharing similar spatial tuning and similar temporal profiles of activation across task epochs. The dependence of correlated discharge on the functional properties of neurons was observed both when we analyzed firing from the task period as well as from baseline fixation. Our results suggest that the coding specificity of individual neurons extends to the local circuits of which they are part.
Differential Contribution of Substance P and Neurokinin A to Spinal Cord Neurokinin-1 Receptor Signaling in the Rat
Authors: Trafton Jodie A. , Abbadie Catherine , Basbaum Allan I.
Published: April 2018

Although the tachykinins substance P (SP) and neurokinin A (NKA) are coreleased from primary afferent nociceptors and act via neurokinin (NK) receptors, their differential effectsin vivoare not known. Despite pharmacological evidence that NKA preferentially binds NK-2 receptors, this receptor is not found in spinal cord neurons. Thus, in the present studies, we compared the extent to which SP and NKA contribute to spinal nociceptive processing via the NK-1 receptor.

We found that SP and NKA induce NK-1 receptor internalization with identical dose dependence and induce increases in intracellular calcium at the same concentrations, suggesting that SP and NKA equally activate the NK-1 receptor. We found, however, that the selective NK-1 receptor antagonist GR 205171 blocked NKA but not SP-induced NK-1 receptor internalization in the rat spinal cordin vivoand in embryonic day 19 rat spinal neuronsin vitro. Using this selectivity of GR 205171 for NKA-induced NK-1 receptor activation, we examined the relative contribution of SP and NKA to noxious stimulus-induced activation of spinal NK-1 receptors. We estimate that NKA contributes to at least 50% of the NK-1 receptor activation in lamina I. Under inflammatory conditions, all noxious stimulus-induced NK-1 receptor internalization in deep dorsal horn neurons was blocked by GR 205171, suggesting that it is entirely NKA-mediated. Substance P-mediated NK-1 receptor internalization was focused at the site of termination of stimulated nociceptors but NKA also activated NK-1 receptors at more distant sites. We conclude that NKA not only targets the NK-1 receptor but may be a predominant pronociceptive primary afferent neurotransmitter.
Susceptibility to Kindling and Neuronal Connections of the Anterior Claustrum
Authors: Zhang Xia , Hannesson Darren K. , Saucier Deborah M. , Wallace Amy E. , Howland John , Corcoran Michael E.
Published: April 2018

The claustrum has been implicated in the kindling of generalized seizures from limbic sites. We examined the susceptibility of the anterior claustrum itself to kindling and correlated this with an anatomical investigation of its afferent and efferent connections.

Electrical stimulation of the anterior claustrum resulted in a pattern of rapid kindling with two distinct phases. Early kindling involved extremely rapid progression to bilaterally generalized seizures of short duration. With repeated daily kindling stimulations, early-phase generalized seizures abruptly became more elaborate and prolonged, resembling limbic-type seizures as triggered from the amygdala. We suggest that the rapid rate of kindling from the anterior claustrum is an indication that the claustrum is functionally close to the mechanisms of seizure generalization.

In support of our hypothesis, we found significant afferent, efferent, and often reciprocal connections between the anterior claustrum and areas that have been implicated in the generation of generalized seizures, including frontal and motor cortex, limbic cortex, amygdala, and endopiriform nucleus. Additional connections were found with various other structures, including olfactory areas, nucleus accumbens, midline thalamus, and brainstem nuclei including the substantia nigra and the dorsal raphe nucleus. The anatomical connections of the anterior claustrum are consistent with its very high susceptibility to kindling and support the view that the claustrum is part of a forebrain network of structures participating in the generalization of seizures.
Time-Dependent Reversal of Long-Term Potentiation by Low-Frequency Stimulation at the Hippocampal Mossy Fiber–CA3 Synapses
Authors: Chen Yea-Lin , Huang Chiung-Chun , Hsu Kuei-Sen
Published: April 2018

Using mouse hippocampal slices, we studied the induction of depotentiation of long-term potentiation (LTP) at the mossy fiber synapses onto CA3 pyramidal neurons. A long train of low-frequency (1 Hz/900 pulses) stimulation (LFS) induced a long-term depression of baseline synaptic transmission or depotentiation of previously established LTP, which was reversible and was independent of NMDA receptor activation. This LFS-induced depotentiation was observed when the stimulus was delivered 1 or 10 min after LTP induction. However, when LFS was applied at 30 min after induction, significantly less depotentiation was found. The induction of depotentiation on one input was associated with a heterosynaptic reverse of the LTP induced previously on a separate pathway. In addition, this LFS-induced depotentiation appeared to be mediated by the activation of group 2 metabotropic glutamate receptors (mGluRs), because it was mimicked by the bath-applied group 2 agonist (2S,2′R,3′R)-2-(2′, 3′-dicarboxycyclopropyl) glycine and was specifically inhibited by the group 2 antagonists (S)-α-methyl-4-carboxyphenylglycine and (αS)-α-amino-α-(1S,2S)-2-carboxycyclopropyl-9H-xanthine-9-propanic acid. Moreover, the induction of depotentiation was entirely normal when synaptic transmission is blocked by glutamate receptor antagonist kynurenic acid and was associated with a reversal of paired-pulse facilitation attenuation during LTP expression. Pretreatment of the hippocampal slices with Gi/o-protein inhibitor pertussis toxin (PTX) prevented the LFS-induced depotentiation. These results suggest that the activation of presynaptic group 2 mGluRs and in turn triggering a PTX-sensitive Gi/o-protein-coupled signaling cascade may contribute to the LFS-induced depotentiation at the mossy fiber–CA3 synapses.
Membrane Resonance and Subthreshold Membrane Oscillations in Mesencephalic V Neurons: Participants in Burst Generation
Authors: Wu Nanping , Hsiao Chie-Fang , Chandler Scott H.
Published: April 2018

Trigeminal mesencephalic (Mes V) neurons are critical components of the circuits controlling oral-motor activity. The possibility that they can function as interneurons necessitates a detailed understanding of the factors controlling their soma excitability. Using whole-cell patch-clamp recording,in vitro, we investigated the development of the ionic mechanisms responsible for the previously described subthreshold membrane oscillations and rhythmical burst discharge in Mes V neurons from rats ages postnatal day (P) 2–12. We found that the oscillation amplitude and frequency increased during development, whereas bursting emerged after P6. Furthermore, when bursting was initiated, the spike frequency was largely determined by the oscillation frequency. Frequency domain analysis indicated that these oscillations emerged from the voltage-dependent resonant properties of Mes V neurons. Low doses of 4-aminopyridine (<100 μm) reduced the oscillations and abolished resonance in most neurons, suggesting that the resonant current is a steady-state K+current (I4-AP). Sodium ion replacement or TTX reduced substantially the oscillations and peak amplitude of the resonance, suggesting the presence of a persistent Na+current (INaP) that functions to amplify the resonance and facilitate the emergence of subthreshold oscillations and bursting.
Protective Autoimmunity Is a Physiological Response to CNS Trauma
Authors: Yoles Eti , Hauben Ehud , Palgi Orna , Agranov Evgenia , Gothilf Amalia , Cohen Avi , Kuchroo Vijay , Cohen Irun R. , Weiner Howard , Schwartz Michal
Published: April 2018

Primary damage caused by injury to the CNS is often followed by delayed degeneration of initially spared neurons. Studies in our laboratory have shown that active or passive immunization with CNS myelin-associated self-antigens can reduce this secondary loss. Here we show, using four experimental paradigms in rodents, that CNS trauma spontaneously evokes a beneficial T cell-dependent immune response, which reduces neuronal loss. (1) Survival of retinal ganglion cells in rats was significantly higher when optic nerve injury was preceded by an unrelated CNS (spinal cord) injury. (2) Locomotor activity of rat hindlimbs (measured in an open field using a locomotor rating scale) after contusive injury of the spinal cord (T8) was significantly better (by three to four score grades) after passive transfer of myelin basic protein (MBP)-activated splenocytes derived from spinally injured rats than in untreated injured control rats or rats similarly treated with splenocytes from naive animals or with splenocytes from spinally injured rats activatedex vivowith ovalbumin or without anyex vivoactivation. (3) Neuronal survival after optic nerve injury was 40% lower in adult rats devoid of mature T cells (caused by thymectomy at birth) than in normal rats. (4) Retinal ganglion cell survival after optic nerve injury was higher (119 ± 3.7%) in transgenic mice overexpressing a T cell receptor (TcR) for MBP and lower (85 ± 1.3%) in mice overexpressing a T cell receptor for the non-self antigen ovalbumin than in matched wild types. Taken together, the results imply that CNS injury evokes a T cell-dependent neuroprotective response.
Dopamine D4Receptor-Deficient Mice Display Cortical Hyperexcitability
Authors: Rubinstein Marcelo , Cepeda Carlos , Hurst Raymond S. , Flores-Hernandez Jorge , Ariano Marjorie A. , Falzone Tomás L. , Kozell Laura B. , Meshul Charles K. , Bunzow James R. , Low Malcolm J. , Levine Michael S. , Grandy David K.
Published: April 2018

The dopamine D4receptor (D4R) is predominantly expressed in the frontal cortex (FC), a brain region that receives dense input from midbrain dopamine (DA) neurons and is associated with cognitive and emotional processes. However, the physiological significance of this dopamine receptor subtype has been difficult to explore because of the slow development of D4R agonists and antagonists the selectivity and efficacy of which have been rigorously demonstratedin vivo. We have attempted to overcome this limitation by taking a multidimensional approach to the characterization of mice completely deficient in this receptor subtype. Electrophysiological current and voltage-clamp recordings were performed in cortical pyramidal neurons from wild-type and D4R-deficient mice. The frequency of spontaneous synaptic activity and the frequency and duration of paroxysmal discharges induced by epileptogenic agents were increased in mutant mice. Enhanced synaptic activity was also observed in brain slices of wild-type mice incubated in the presence of the selective D4R antagonist PNU-101387G. Consistent with greater electrophysiological activity, nerve terminal glutamate density associated with asymmetrical synaptic contacts within layer VI of the motor cortex was reduced in mutant neurons. Taken together, these results suggest that the D4R can function as an inhibitory modulator of glutamate activity in the FC.
Bipartite Interaction between Neurofibromatosis Type I Protein (Neurofibromin) and Syndecan Transmembrane Heparan Sulfate Proteoglycans
Authors: Hsueh Yi-Ping , Roberts Anne M. , Volta Manuela , Sheng Morgan , Roberts Roland G.
Published: April 2018

The neurofibromatosis type 1 (NF1) gene encodes a large tumor suppressor protein (neurofibromin). Although it is known to possess Ras GTPase-activating protein (GAP) activity, the cellular role of neurofibromin remains unclear. Here we used yeast two-hybrid screening to identify neurofibromin-interacting proteins. Syndecan-2, a transmembrane heparan sulfate proteoglycan (HSPG), was isolated as a binding partner for two distinct regions of the neurofibromin protein. We subsequently found that neurofibromin can bind all four mammalian syndecans. NF1 interaction requires the transmembrane domain and a membrane-proximal region of the cytoplasmic tail of syndecan, but not the C terminus of syndecan known to bind to CASK, a membrane-associated guanylate kinase (MAGUK). Neurofibromin, syndecans, and CASK have overlapping subcellular distributions in axons and synapses of neurons, as shown by biochemical fractionation and immunostaining. Moreover, neurofibromin exists in a complex with syndecan and CASKin vivo, as evidenced by their coimmunoprecipitation from rat brain. Our findings suggest that interaction with different members of the syndecan family may be a mechanism for localizing neurofibromin to specialized domains of the plasma membrane.
Metabotropic Glutamate Receptor Subtypes 1 and 5 Are Activators of Extracellular Signal-Regulated Kinase Signaling Required for Inflammatory Pain in Mice
Authors: Karim Farzana , Wang Chia-Chuan , Gereau Robert W.
Published: April 2018

Metabotropic glutamate receptors are expressed abundantly in the spinal cord and have been shown to play important roles in the modulation of nociceptive transmission and plasticity. Most previous studies have focused on the group I metabotropic glutamate receptors (mGluR1 and mGluR5) and activation of phospholipase C signaling by these receptors in modulating nociception. Recently, it was shown that the extracellular signal-regulated kinases (ERKs)/mitogen-activated protein kinases are activated in spinal cord dorsal horn neurons in response to stimulation of nociceptors and that ERK signaling is involved in nociceptive plasticity. In the present studies, we sought to test the hypothesis that group I mGluRs modulate nociceptive transmission or plasticity via modulation of ERK signaling in dorsal horn neurons. We show that activation of mGluR1 and mGluR5 leads to activation of ERK1 and ERK2 in the spinal cord. Furthermore, we find that inflammation-evoked ERK activation, which is required for nociceptive plasticity, is downstream of mGluR1 and mGluR5. Finally, we show colocalization of group I mGluRs with activated ERK in dorsal horn neurons. These results show that mGluR1 and mGluR5 are activated in dorsal horn neurons in response to peripheral inflammation and that activation of these group I mGluRs leads to activation of ERK1 and ERK2, resulting in enhanced pain sensitivity.
A Distal Upstream Enhancer from theMyelin Basic ProteinGene Regulates Expression in Myelin-Forming Schwann Cells
Authors: Forghani Reza , Garofalo Lorella , Foran David R. , Farhadi Hooman F. , Lepage Pierre , Hudson Thomas J. , Tretjakoff Irene , Valera Priscila , Peterson Alan
Published: April 2018

In peripheral nerves, large caliber axons are ensheathed by myelin-elaborating Schwann cells. Multiple lines of evidence demonstrate that expression of the genes encoding myelin structural proteins occurs in Schwann cells in response to axonal instructions. To gain further insight into the mechanisms controlling myelin gene expression, we used reporter constructs in transgenic mice to search for the DNA elements that regulate themyelin basic protein(MBP) gene. Through thisin vivoinvestigation, we provide evidence for the participation of multiple, widely distributed, positive and negative elements in the overall control ofMBPexpression. Notably, all constructs bearing a 0.6 kb far-upstream sequence, designated Schwann cell enhancer 1 (SCE1), expressed at high levels in myelin-forming Schwann cells. In addition, robust targeting activity conferred by SCE1 was shown to be independent of otherMBP5′ flanking sequence. These observations suggest that SCE1 will make available a powerful tool to drive transgene expression in myelinating Schwann cells and that a focused analysis of the SCE1 sequence will lead to the identification of transcription factor binding sites that positively regulateMBPexpression.
Widespread Expression of Netrin-1 by Neurons and Oligodendrocytes in the Adult Mammalian Spinal Cord
Authors: Manitt Colleen , Colicos Michael A. , Thompson Katherine M. , Rousselle Etienne , Peterson Alan C. , Kennedy Timothy E.
Published: April 2018

Netrins are a family of secreted proteins that function as chemotropic axon guidance cues during neural development. Here we demonstrate that netrin-1 continues to be expressed in the adult rat spinal cord at a level similar to that in the embryonic CNS. In contrast, netrin-3, which is also expressed in the embryonic spinal cord, was not detected in the adult.In situhybridization analysis demonstrated that cells in the white matter and the gray matter of the adult spinal cord express netrin-1. Colocalization studies using the neuronal marker NeuN revealed that netrin-1 is expressed by multiple classes of spinal interneurons and motoneurons. Markers identifying glial cell types indicated that netrin-1 is expressed by most, if not all, oligodendrocytes but not by astrocytes. During neural development, netrin-1 has been proposed to function as a diffusible long-range cue for growing axons. We show that in the adult spinal cord the majority of netrin-1 protein is not freely soluble but is associated with membranes or the extracellular matrix. Fractionation of adult spinal cord white matter demonstrated that netrin-1 was absent from fractions enriched for compact myelin but was enriched in fractions containing periaxonal myelin and axolemma, indicating that netrin-1 protein may be localized to the periaxonal space. These findings suggest that in addition to its role as a long-range guidance cue for developing axons, netrin may have a short-range function associated with the cell surface that contributes to the maintenance of appropriate neuronal and axon–oligodendroglial interactions in the mature nervous system.
Rules of Connectivity between Geniculate Cells and Simple Cells in Cat Primary Visual Cortex
Authors: Alonso Jose-Manuel , Usrey W. Martin , Reid R. Clay
Published: April 2018

Hundreds of thalamic axons ramify within a column of cat visual cortex; yet each layer 4 neuron receives input from only a fraction of them. We have examined the specificity of these connections by recording simultaneously from layer 4 simple cells and cells in the lateral geniculate nucleus with spatially overlapping receptive fields (n= 221 cell pairs). Because of the precise retinotopic organization of visual cortex, the geniculate axons and simple-cell dendrites of these cell pairs should have overlapped within layer 4. Nevertheless, monosynaptic connections were identified in only 33% of all cases, as estimated by cross-correlation analysis. The visual responses of monosynaptically connected geniculate cells and simple cells were closely related. The probability of connection was greatest when a geniculate center overlapped a strong simple-cell subregion of the same sign (ON or OFF) near the center of the subregion. This probability was further increased when the time courses of the visual responses were similar. In addition, the connections were strongest when the simple-cell subregion and the geniculate center were matched in position, sign, and size. The rules of connectivity between geniculate afferents and simple cells resemble those found for retinal afferents to geniculate cells. The connections along the retinogeniculocortical pathway, therefore, show a precision that goes beyond simple retinotopy to include many other response properties, such as receptive-field sign, timing, subregion strength, and size. This specificity in wiring emphasizes the need for developmental mechanisms (presumably correlation-based) that can select among afferents that differ only slightly in their response properties.
Tonic Control of Peripheral Cutaneous Nociceptors by Somatostatin Receptors
Authors: Carlton Susan M. , Du Junhui , Zhou Shengtai , Coggeshall Richard E.
Published: April 2018

The peptide somatostatin [somatotropin release-inhibiting factor (SRIF)] is widely distributed in the body and exerts a variety of hormonal and neural actions. Several lines of evidence indicate that SRIF is important in nociceptive processing: (1) it is localized in a subset of small-diameter dorsal root ganglion cells; (2) activation of SRIF receptors results in inhibition of both nociceptive behaviors in animals and acute and chronic pain in humans; (3) SRIF inhibits dorsal horn neuronal activity; and (4) SRIF reduces responses of joint mechanoreceptors to noxious rotation of the knee joint. The goal of the present study is to show that cutaneous nociceptors are under the tonic inhibitory control of SRIF. This is accomplished using behavioral and electrophysiological paradigms. In a dose-dependent manner, intraplantar injection of the SRIF receptor antagonist cyclo-somatostatin (c-SOM) results in nociceptive behaviors in normal animals and enhancement of nociceptive behaviors in formalin-injected animals, and these actions can be blocked when c-SOM is coapplied with three different SRIF agonists. Furthermore, intraplantar injection of SRIF antiserum also results in nociceptive behaviors. Electrophysiological recordings using anin vitroglabrous skin–nerve preparation show increased nociceptor activity in response to c-SOM, and this increase is blocked by the same three SRIF agonists. Parallel behavioral and electrophysiological studies using the opioid antagonist naloxone demonstrate that endogenous opioids do not maintain a tonic inhibitory control over peripheral nociceptors, nor does opioid receptor antagonism influence peripheral SRIF effects on nociceptors. These findings demonstrate that SRIF receptors maintain a tonic inhibitory control over peripheral nociceptors, and this may contribute to mechanisms that control the excitability of these terminals.
Progressive Enhancement of Delayed Hyperalgesia Induced by Repeated Heroin Administration: A Sensitization Process
Authors: Célèrier Evelyne , Laulin Jean-Paul , Corcuff Jean-Benoı̂t , Le Moal Michel , Simonnet Guy
Published: April 2018

It is difficult to conceive that tolerance and sensitization processes, two apparently opposite phenomena, can concomitantly modify one given biological process, i.e., the processing of pain. We have shown recently that opiates produce not only analgesia but also long-lasting hyperalgesia in rats. This suggests that tolerance to the analgesic effect of an opiate, especially heroin, could be in part the result of an actual sensitization of pronociceptive systems. Here, we show that both magnitude and duration of heroin-induced delayed hyperalgesia increase with intermittent heroin administrations, leading to an apparent decrease in the analgesic effectiveness of a given heroin dose. Our observation that a small dose of heroin which is ineffective for triggering a delayed hyperalgesia in non-heroin-treated rats induced an enhancement in pain sensitivity for several days after a series of heroin administrations is in agreement with the sensitization hypothesis. The effectiveness of the opioid receptor antagonist naloxone to precipitate hyperalgesia in rats that had recovered their pre-drug nociceptive value after single or repeated heroin administrations indicates that heroin-deprived rats were in a new biological state associated with a high level balance between opioid-dependent analgesic systems and pronociceptive systems. Because the NMDA receptor antagonist dizocilpine maleate (MK-801) prevented both heroin-induced long-lasting enhancement in pain sensitivity and naloxone-precipitated hyperalgesia, these findings further suggest that tolerance, sensitization, and one withdrawal symptom, hyperalgesia, are issued from a neuroadaptive process in which NMDA systems play a critical role.
Dopamine Attenuates Prefrontal Cortical Suppression of Sensory Inputs to the Basolateral Amygdala of Rats
Authors: Rosenkranz J. Amiel , Grace Anthony A.
Published: April 2018

The basolateral complex of the amygdala (BLA) plays a significant role in affective behavior that is likely regulated by afferents from the medial prefrontal cortex (mPFC). Studies suggest that dopamine (DA) is a necessary component for production of appropriate affective responses. In this study, prefrontal cortical and sensory cortical [temporal area 3 (Te3)] inputs to the BLA and their modulation by DA receptor activation was examined usingin vivosingle-unit extracellular recordings. We found that Te3 inputs are more capable of driving BLA projection neuron firing, whereas mPFC inputs potently elicited firing from BLA interneurons. Moreover, mPFC stimulation before Te3 stimulation attenuated the probability of Te3-evoked spikes in BLA projection neurons, possibly via activation of inhibitory interneurons. DA receptor activation by apomorphine attenuated mPFC inputs, while augmenting Te3 inputs. Additionally, DA receptor activation suppressed mPFC-induced inhibition of Te3-evoked spikes. Thus, the mPFC may attenuate sensory-driven amygdala-mediated affective responses via recruitment of BLA inhibitory interneurons that suppress sensory cortical inputs. In situations of enhanced DA levels in the BLA, such as during stress and after amphetamine administration, mPFC regulation of BLA will be dampened, leading to a disinhibition of sensory-driven affective responses.
Amygdalar NMDA Receptors Are Critical for the Expression of Multiple Conditioned Fear Responses
Authors: Lee Hongjoo J. , Choi June-Seek , Brown Thomas H. , Kim Jeansok J.
Published: April 2018

There is conflicting evidence regarding the issue of whether NMDA receptors in the basolateral amygdalar complex (BLA) are critically involved in the expression of conditioned fear. This matter was addressed by infusing the rat BLA withd,l-2-amino-5-phosphonovaleric acid (APV), a competitive NMDA receptor antagonist. APV infusion into the BLA was reported to block the expression of conditioned fear when measured by freezing but not when measured by fear-potentiated startle response to a loud noise. To examine this issue further, here we used multiple indices of conditioned fear, including analgesia, 22 kHz ultrasonic vocalization (USV), defecation, and freezing. Rats with bilateral BLA cannula implants underwent fear conditioning consisting of 10 tone–footshock pairings. Before context and tone fear-retention tests, animals received intra-BLA infusions with APV (2.5 μg/side) or artificial CSF. Both tone and context tests demonstrated that the expression of conditioned freezing, USV, defecation, and analgesia were significantly impaired by intra-amygdalar infusions of APV. In a second set of experiments, intra-BLA infusions of APV markedly impaired the normal expression of postshock fear responses during training, as measured by freezing, USV, and defecation. Immediate postshock fear expression was predictive of subsequent fear retention to the tone and context when the animals were not infused. These results are consistent with the hypothesis that amygdalar NMDA receptors participate in normal synaptic transmission and therefore the overall functioning of the amygdala.
Extracellular Nucleotides Differentially Regulate Interleukin-1β Signaling in Primary Human Astrocytes: Implications for Inflammatory Gene Expression
Authors: John Gareth R. , Simpson Julie E. , Woodroofe M. Nicola , Lee Sunhee C. , Brosnan Celia F.
Published: April 2018

The cytokine interleukin-1β (IL-1β) is a potent activator of human astrocytes, inducing or modulating expression of multiple proinflammatory genes via activation of the transcription factors nuclear factor-κB (NF-κB) and activator protein-1 (AP-1). In this study, we examined whether IL-1β signaling is regulated in these cells by extracellular nucleotides that are released at high concentrations under inflammatory conditions and act as ligands for members of the P2 receptor family. Using reporter constructs and electromobility shift assays, we found that cotreatment of astrocyte cultures with ATP (1–100 μm) significantly potentiated IL-1β-mediated activation of NF-κB and AP-1 and that ATP alone activated AP-1. These effects were blocked by the P2 receptor antagonists XAMR 0721, periodate-oxidized ATP, and suramin. A role for ATP in modulating IL-1β-mediated inflammatory gene expression was supported further by the observation that ATP potentiated the IL-1β-induced expression of IL-8 mRNA and protein but strongly downregulated IP-10 expression. Reverse transcription-PCR and cloning demonstrated expression of the ATP-responsive P2 receptor subtypes P2Y1, P2Y2, and P2X7, as well as the ATP-insensitive receptor P2Y4. ADP, a selective agonist for P2Y1, produced results similar to or greater than those obtained using ATP, whereas 2′-3′-O-(4-benzoyl-benzoyl)-ATP, a selective agonist for P2X7, was less effective than ATP. In contrast, UTP, a selective agonist for P2Y2and P2Y4, was ineffective. These studies indicate that different P2 receptor subtypes play distinct roles in the modulation of IL-1β-mediated signal transduction in human astrocytes, and that signaling via P2 receptors may fine-tune the transcription of genes involved in inflammatory responses in the human CNS.