bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of Convergent Thalamocortical and Intracortical Synaptic Potentials in Single Neurons of Neocortex
Authors: Gil Ziv , Amitai Yael
Published: April 2018

We explored differences in the properties of convergent afferent inputs to single neurons in the barrel area of the neocortex. Thalamocortical slices were prepared from mature mice. Recordings were made from neurons in layer V, and either thalamocortical afferents or horizontal intracortical axons were stimulated. Monosynaptic EPSPs from both sources had latencies shorter than 1.8 msec and low shape variance. Disynaptic thalamocortical IPSPs had latencies longer than 1.8 msec. All neuronal types, as defined by intrinsic firing patterns, received both thalamocortical and intracortical monosynaptic input. The shape parameters (rate of rise and half-width) of monosynaptic EPSPs from the two inputs did not differ significantly. The rate of rise of EPSPs varied considerably across cells, but the rates of rise of thalamocortical and intracortical EPSPs onto single cells were strongly correlated.

The relative thresholds for activation of synaptic excitation and inhibition were strikingly different between the two tracts: thalamocortical stimulation induced GABAA-dependent IPSPs at stimulus intensities equal to or less than those required for evoking EPSPs in 35% (24 of 68) of the cells. In contrast, the threshold response to intracortical stimulation was always an EPSP, and only stronger stimuli could generate di- or polysynaptic IPSPs.

We suggest that postsynaptic factors may tend to equalize the waveforms of EPSPs from thalamocortical and intracortical synapses onto single neurons. A major difference between the two convergent tracts is that the thalamocortical pathway much more effectively activates feedforward inhibitory circuits than does the horizontal intracortical pathway.
Differential Survival of Cajal–Retzius Cells in Organotypic Cultures of Hippocampus and Neocortex
Authors: Del Rı́o José A. , Heimrich Bernd , Supèr Hans , Borrell Vı́ctor , Frotscher Michael , Soriano Eduardo
Published: April 2018

Cajal–Retzius (CR) cells are transient, pioneer neurons of layer I of the cortex that are believed to play essential roles in corticogenesis, e.g., in neuronal migration and synaptogenesis. Here we have used calretinin immunostaining to study the characteristics, survival, and fate of CR cells in single organotypic slice cultures of mouse neocortex and hippocampus deprived of their extrinsic afferents. In neocortical explants, CR cells were observed after 1–3 din vitro(DIV), but they disappeared after 5–7 DIV, which is similar to their time of degenerationin vivo. The disappearance of CR cells in neocortical slices was prevented by incubation with tetrodotoxin and the glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3,-dione but not by 2-amino-5-phosphonopentanoic acid, suggesting that neuronal activity and non-NMDA glutamate receptors may trigger CR cell death in the neocortex.

In contrast to the situationin vivo, in which many hippocampal CR cells disappear at approximately the third postnatal week, CR cells survived in single hippocampal cultures after long incubation times (31 DIV), with their morphology essentially unaltered. In contrast, fewer CR cells were found when hippocampal slices were cocultured with explants from the entorhinal cortex. Because CR cells are transient synaptic targets for entorhinohippocampal afferents, these findings suggest a role for entorhinal afferents in the degeneration of CR cells in the hippocampus. In conclusion, this study shows different survival properties of CR cells in organotypic slice cultures of hippocampus and neocortex, and it suggests that different mechanisms are involved in the regulation of the process of naturally occurring CR cell death in the two cortical regions.
Atrial Natriuretic Peptide Modulates Synaptic Transmission from Osmoreceptor Afferents to the Supraoptic Nucleus
Authors: Richard Dominique , Bourque Charles W.
Published: April 2018

Atrial natriuretic peptide (ANP) and its receptors are present in hypothalamic nuclei containing the magnocellular neurosecretory cells (MNCs), which release vasopressin and oxytocin. In the rat, intracerebroventricular injections of ANP inhibit the release of both hormones in response to hypertonicity. Although these findings suggest a role for endogenous ANP in the central control of fluid balance, cellular mechanisms underlying the modulatory actions of ANP are unknown. We therefore examined the effects of ANP on the osmoresponsiveness of MNCs impaled in rat hypothalamic explants. Applications of ANP (75–150 nm) over the supraoptic nucleus did not affect depolarizing responses to local hypertonicity, but they reversibly abolished the synaptic excitation of MNCs after hypertonic stimulation of the organum vasculosum laminae terminalis (OVLT). These effects were associated with decreased spontaneous EPSP (sEPSP) amplitude rather than with changes in sEPSP frequency. Accordingly, application of ANP reduced the amplitude of glutamatergic EPSPs evoked by electrical stimulation of the OVLT (IC50∼ 3 nm). The inhibitory effects of ANP on EPSP amplitude were mimicked by application of 3′-5′-dibutyryl cGMP, consistent with the guanylate cyclase activity of natriuretic peptide receptors. Although depolarizing responses of MNCs to ionotropic glutamate receptor agonists were unaffected by ANP, the peptide reversibly enhanced paired-pulse facilitation of electrically evoked EPSPs. These results indicate that centrally released ANP may inhibit osmotically evoked neurohypophysial hormone release through presynaptic inhibition of glutamate release from osmoreceptor afferents derived from the OVLT.
Behavioral Analysis of Signals that Guide Learned Changes in the Amplitude and Dynamics of the Vestibulo-Ocular Reflex
Authors: Raymond Jennifer L. , Lisberger Stephen G.
Published: April 2018

We characterized the dependence of motor learning in the monkey vestibulo-ocular reflex (VOR) on the duration, frequency, and relative timing of the visual and vestibular stimuli used to induce learning. The amplitude of the VOR was decreased or increased through training with paired head and visual stimulus motion in the same or opposite directions, respectively. For training stimuli that consisted of simultaneous pulses of head and target velocity 80–1000 msec in duration, brief stimuli caused small changes in the amplitude of the VOR, whereas long stimuli caused larger changes in amplitude as well as changes in the dynamics of the reflex. When the relative timing of the visual and vestibular stimuli was varied, brief image motion paired with the beginning of a longer vestibular stimulus caused changes in the amplitude of the reflex alone, but the same image motion paired with a later time in the vestibular stimulus caused changes in the dynamics as well as the amplitude of the VOR. For training stimuli that consisted of sinusoidal head and visual stimulus motion, low-frequency training stimuli induced frequency-selective changes in the VOR, as reported previously, whereas high-frequency training stimuli induced changes in the amplitude of the VOR that were more similar across test frequency. The results suggest that there are at least two distinguishable components of motor learning in the VOR. One component is induced by short-duration or high-frequency stimuli and involves changes in only the amplitude of the reflex. A second component is induced by long-duration or low-frequency stimuli and involves changes in the amplitude and dynamics of the VOR.
Neuronal Nicotinic Receptor Expression in Sensory Neurons of the Rat Trigeminal Ganglion: Demonstration of α3β4, a Novel Subtype in the Mammalian Nervous System
Authors: Flores Christopher M. , DeCamp Raquel M. , Kilo Sonja , Rogers Scott W. , Hargreaves Kenneth M.
Published: April 2018

The identification of a family of neuronal nicotinic receptor subunit genes establishes the potential for multiple subtypes with diverse physiological functions. Virtually all of the high affinity nicotinic receptors measured to date in the rodent CNS are composed of α4 and β2 subunits only. However, the demonstration of other subunit transcripts in a variety of central and peripheral nervous tissues suggests a greater degree of receptor subtype heterogeneity than so far has been elucidated. The purpose of the present studies was to determine at the mRNA and protein levels which neuronal nicotinic receptor subunits are expressed by sensory neurons of the rat trigeminal ganglion and in what combinations these gene products associate to form neuronal nicotinic receptor subtypes in this tissue. Radioreceptor binding analysis indicated that in the adult rat trigeminal ganglion there exist at least two nicotinic receptor binding sites with differing affinities for [3H]-epibatidine.In situhybridization histochemical studies revealed the existence of mRNA encoding the α3, α4, α5, β2, and β4 subunits, but not the α2 subunit. Immunoprecipitation with subunit-specific antisera demonstrated that each of the subunits present in the ganglion at the mRNA level is a constituent of nicotinic receptors capable of binding3H-epibatidine. Various applications of these approaches yielded strong evidence that, in addition to α4β2, which is thought to be the predominant neuronal nicotinic receptor subtype in the rodent CNS, trigeminal sensory neurons express as the principal subtype α3β4, which has not been demonstrated previously in mammalian nervous tissue.
Effects of Chronic Treatment with Δ9-Tetrahydrocannabinol on Cannabinoid-Stimulated [35S]GTPγS Autoradiography in Rat Brain
Authors: Sim Laura J. , Hampson Robert E. , Deadwyler Sam A. , Childers Steven R.
Published: April 2018

Chronic Δ9-tetrahydrocannabinol (Δ9-THC) administration produces tolerance to cannabinoid effects, but alterations in signal transduction that mediate these changes are not yet known. The present study usesin vitroautoradiography of agonist-stimulated [35S]GTPγS binding to localize cannabinoid receptor-activated G-proteins after chronic Δ9-THC treatment. Cannabinoid (WIN 55212-2)-stimulated [35S]GTPγS binding was performed in brain sections from rats treated chronically with 10 mg/kg Δ9-THC for 21 d. Control animals received saline or an acute injection of Δ9-THC. Acute Δ9-THC treatment had no effect on basal or WIN 55212-2-stimulated [35S]GTPγS binding. After chronic Δ9-THC treatment, net WIN 55212-2-stimulated [35S]GTPγS binding was reduced significantly (up to 70%) in most brain regions, including the hippocampus, caudate-putamen, perirhinal and entorhinal cortex, globus pallidus, substantia nigra, and cerebellum. In contrast, chronic Δ9-THC treatment had no effect on GABAB-stimulated [35S]GTPγS binding. In membranes and brain sections, Δ9-THC was a partial agonist, stimulating [35S]GTPγS by only 20% of the level stimulated by WIN 55212-2 and inhibiting WIN 55212-2-stimulated [35S]GTPγS at high concentrations. Because the EC50of WIN 55212-2-stimulated [35S]GTPγS binding and theKDof cannabinoid receptor binding were unchanged by chronic Δ9-THC treatment, the partial agonist actions of Δ9-THC did not produce the decrease in cannabinoid-stimulated [35S]GTPγS binding. These results suggest that profound desensitization of cannabinoid-activated signal transduction mechanisms occurs after chronic Δ9-THC treatment.
17α-Estradiol Exerts Neuroprotective Effects on SK-N-SH Cells
Authors: Green Pattie S. , Bishop Jean , Simpkins James W.
Published: April 2018

Estradiol (E2) has been shown to exert organizational, neurotrophic, and neuroprotective effects in the CNS. The present study assessed the specificity of the neuroprotective effects of estradiol for the potent 17β-isomer. SK-N-SH cells from a human neuroblastoma cell line, which we have shown to be estrogen-responsive, were cultured at low or high plating density. Then cells were exposed to 17β-E2 (0.2 or 2 nm), 17α-E2 (0.2 or 2 nm), or cholesterol, testosterone, dihydrotestosterone, progesterone, or corticosterone (all at 2 nm). Cultures were insulted by serum deprivation, which caused a profound loss of cells. At 1 or 2 d of serum deprivation and steroid hormone replacement, the protection afforded cells by the steroid addition was assessed. Serum deprivation killed ∼90% of cells cultured at both low and high plating density. Both 17α- and 17β-E2 provided protection of SK-N-SH cells at either plating density. Further, a 10-fold molar excess of tamoxifen antagonized only approximately one-third of the neuroprotective effects of either isomer of estradiol, and a 100-fold excess of tamoxifen had no additional effect on the neuroprotection by 17β-E2. By contrast, none of the other steroids tested protected cells from the insult of serum deprivation. These results indicate that the neuroprotective effects of estrogens are not attributable to the general steroid structure, and the majority of the neuroprotection may not be mediated via a tamoxifen-antagonized receptor mechanism.
Nerve Growth Factor Induces Apoptosis in Human Medulloblastoma Cell Lines that Express TrkA Receptors
Authors: Muragaki Yoshihiro , Chou Thomas T. , Kaplan David R. , Trojanowski John Q. , Lee Virginia M.-Y.
Published: April 2018

Neurotrophins act through their cognate receptors to promote the differentiation and/or survival of neuronal progenitor cells, immature neurons, and other cells. Here, we examined the effects of nerve growth factor (NGF) and its cognate receptor (Trk or TrkA) on the survival of a common childhood brain tumor, i.e., medulloblastoma, a tumor that resembles CNS neuroepithelial progenitor cells. To do this, we engineered two human medulloblastoma cell lines (i.e., D283MED and DAOY cells) to express human TrkA using a retroviral expression vector. Surprisingly, NGF-treated medulloblastoma cells expressing the TrkA receptor (D283trk and DAOYtrk cells) grown in the presence or absence of serum underwent massive apoptosis, but similar treatment did not induce apoptosis in wild-type uninfected cells, cells expressing an empty vector, or cells expressing the TrkC receptor. Furthermore, D283MED cells engineered to express the human p75 NGF receptor (D283p75) also did not undergo apoptosis. Significantly, NGF-induced apoptosis in D283trk and DAOYtrk cells can be inhibited by anti-NGF antibodies and by K-252a, an inhibitor of TrkA tyrosine phosphorylation and mimicked by high concentrations of NT3. Because NGF treatment primarily eliminated D283trk cells from the S phase of the cell cycle, this form of NGF-mediated apoptosis is cell cycle-dependent. These findings suggest that a NGF/TrkA signal transduction pathway could activate apoptotic cell death programs in CNS neuroepithelial progenitor cells and in childhood brain tumors.
Heterogeneity of Nicotinic Receptor Class and Subunit mRNA Expression among Individual Parasympathetic Neurons from Rat Intracardiac Ganglia
Authors: Poth Kevin , Nutter Thomas J. , Cuevas Javier , Parker Michael J. , Adams David J. , Luetje Charles W.
Published: April 2018

Neurons have the potential to form thousands of distinct neuronal nicotinic receptors from the eight α and three β subunits that currently are known. In an effort to determine how much of this potential complexity is realized among individual neurons, we examined the nicotinic pharmacological and biophysical properties and receptor subunit mRNA expression patterns in individual neurons cultured from rat epicardial ganglia. Analysis of the whole-cell pharmacology of these neurons showed a diversity of responses to the agonists acetylcholine, nicotine, cytisine, and 1,1-dimethyl-4-phenylpiperazinium, suggesting that a heterogeneous population of nicotinic receptor classes, or subtypes, is expressed by individual neurons. Single-channel analysis demonstrated three distinct conductances (18, 24, and 31 pS), with patches from different neurons containing different combinations of these channel classes. We used single-cell RT-PCR to examine nicotinic acetylcholine receptor (nAChR) subunit mRNA expression by individual neurons. Although mRNAs encoding all eight neuronal nAChR subunits for which we probed (α2–α5, α7, β2–β4) were present in multicellular cultures, we found that individual epicardial neurons express distinct subsets of these nAChR subunit mRNAs. These results suggest that individual epicardial neurons express distinct arrays of nAChR subunits and that these subunits may assemble into functional receptors with distinct and variable subunit composition. This variable receptor subunit expression provides an explanation for the diversity of pharmacological and single-channel responses we have observed in individual neurons.
A Transcription-Dependent Switch Controls Competence of Adult Neurons for Distinct Modes of Axon Growth
Authors: Smith Deanna S. , Pate Skene J. H.
Published: April 2018

Although maturing neurons undergo a precipitous decline in the expression of genes associated with developmental axon growth, structural changes in axon arbors occur in the adult nervous system under both normal and pathological conditions. Furthermore, some neurons support extensive regrowth of long axons after nerve injury. Analysis of adult dorsal root ganglion (DRG) neurons in culture now shows that competence for distinct types of axon growth depends on different patterns of gene expression. In the absence of ongoing transcription, newly isolated neurons can extend compact, highly branched arbors during the first day in culture. Neurons subjected to peripheral axon injury 2–7 d before plating support a distinct mode of growth characterized by rapid extension of long, sparsely branched axons. A transition from “arborizing” to “elongating” growth occurs in naive adult neurons after ∼24 hr in culture but requires a discrete period of new transcription after removal of the ganglia from the intact animal. Thus, peripheral axotomy—by nerve crush or during removal of DRGs—induces a transcription-dependent change that alters the type of axon growth that can be executed by these adult neurons. This transition appears to be triggered, in large part, by interruption of retrogradely transported signals, because blocking axonal transportin vivocan elicit competence for elongating growth in many DRG neurons. In contrast to peripheral axotomy, interruption of the centrally projecting axons of DRG neuronsin vivoleads to subsequent growthin vitrothat is intermediate between “arborizing” and “elongating” growth. This suggests that the transition between these two modes of growth is a multistep process and that individual steps may be regulated separately. These observations together suggest that structural remodeling in the adult nervous system need not involve the same molecular apparatus as long axon growth during development and regeneration.
Learning-Dependent Synaptic Modifications in the Cerebellar Cortex of the Adult Rat Persist for at Least Four Weeks
Authors: Kleim Jeffrey A. , Vij Kapil , Ballard David H. , Greenough William T.
Published: April 2018

Several experiments have demonstrated increased synapse number within the cerebellar cortex in association with motor skill learning but not with motor activity alone. The persistence of these synaptic changes in the absence of continued training was examined in the present experiment. Adult female rats were randomly allocated to either an acrobatic condition (AC) or a motor activity condition (MC). The AC animals were trained to traverse a complex series of obstacles, and each AC animal was pair-matched with an MC animal that traversed an obstacle-free runway. These animals were further assigned to one of three training conditions. Animals in the EARLY condition were trained for 10 consecutive days before being killed, animals in the DELAY condition received the same 10 d of training followed by a 28 d period without training, and animals in the CONTINUOUS condition were trained for the entire 38 d. Unbiased stereological techniques were used to obtain estimates of the number of synapses per Purkinje cell within the cerebellar paramedian lobule. Results showed the AC animals to have significantly more synapses per Purkinje cell than the MC animals in all three training conditions. There were no differences in the number of synapses per Purkinje cell among the EARLY, DELAY, and CONTINUOUS conditions. These data demonstrate that both the motor skills and the increases in synapse number presumed to support them persist in the absence of continued training.
Multiple Receptors Involved in Peripheral α2, μ, and A1Antinociception, Tolerance, and Withdrawal
Authors: Aley K. O. , Levine Jon D.
Published: April 2018

We examined the interactions among three classes of peripherally-acting antinociceptive agents (μ-opioid, α2-adrenergic, and A1-adenosine) in the development of tolerance and dependence to their antinociceptive effects. Antinociception was determined by assessing the degree of inhibition of prostaglandin E2(PGE2)-induced mechanical hyperalgesia, using the Randall-Selitto paw-withdrawal test.

Tolerance developed within 4 hr to the antinociceptive effect of the α2-adrenergic agonist clonidine; dependence also occurred at that time, demonstrated as a withdrawal hyperalgesia that was precipitated by the α2-receptor antagonist yohimbine. These findings are similar to those reported previously for tolerance and dependence to μ and A1peripheral antinociception (Aley et al., 1995).

Furthermore, cross-tolerance and cross-withdrawal between μ, A1, and α2agonists occurred. The observations of cross-tolerance and cross-withdrawal suggest that all three receptors are located on the same primary afferent nociceptors. In addition, the observations suggest that the mechanisms of tolerance and dependence to the antinociceptive effects of μ, A1, and α2are mediated by a common mechanism.

Although any of the agonists administered alone produce antinociception, we found that μ, A1, and α2receptors may not act independently to produce antinociception, but rather may require the physical presence of the other receptors to produce antinociception by any one agonist. This was suggested by the finding that clonidine (α2-agonist) antinociception was blocked not only by yohimbine (α2-antagonist) but also by PACPX (A1-antagonist) and by naloxone (μ-antagonist), and that DAMGO (μ-agonist) antinociception and CPA (A1-agonist) antinociception were blocked not only by naloxone (μ-antagonist) and PACPX (A1-antagonist), respectively, but also by yohimbine (α2-antagonist). This cross-antagonism of antinociception occurred at the ID80dose for each antagonist at its homologous receptor. To test the hypothesis that the physical presence of μ-opioid receptor is required not only for μ antinociception but also for α2antinociception, antisense oligodeoxynucleotides (ODNs) for the μ-opioid and α2C-adrenergic receptors were administered intrathecally to reduce the expression of these receptors on primary afferent neurons. These studies demonstrated that μ-opioid ODN administration decreased not only μ-opioid but also α2-adrenergic antinociception; A1antinociception was unaffected. In contrast, α2C-adrenergic ODN decreased antinociception induced by all three classes of antinociceptive agents.

In conclusion, these data suggest that peripheral antinociception induced by μ, α2, and A1agonists requires the physical presence of multiple receptors. We propose that there is a μ, A1, α2receptor complex mediating antinociception in the periphery. In addition, there is cross-tolerance and cross-dependence between μ, A1, and α2antinociception, suggesting that their underlying mechanisms are related.
Quantitative Trait Loci Affecting Methamphetamine Responses in BXD Recombinant Inbred Mouse Strains
Authors: Grisel Judith E. , Belknap John K. , O’Toole L. A. , Helms M. L. , Wenger Charlotte D. , Crabbe John C.
Published: April 2018

Individual differences in most behavioral and pharmacological responses to abused drugs are dependent on both genetic and environmental factors. The genetic influences on the complex phenotypes related to drug abuse have been difficult to study using classical genetic analyses. Quantitative trait locus (QTL) mapping is a method that has been used successfully to examine genetic contributions to some of these traits by correlating allelic variation in polymorphic genetic markers of known chromosomal location with variation in drug-response phenotypes. We evaluated several behavioral responses to multiple doses of methamphetamine (METH) in C57BL/6J (B6), DBA/2J (D2), and 25 of their recombinant inbred (BXD RI) strains. Stereotyped chewing, horizontal home cage activity, and changes in body temperature after 0, 4, 8, or 16 mg/kg METH, as well as stereotyped climbing behavior after 16 mg/kg METH, were examined. Associations (p< 0.01) between METH sensitivity and allelic status at multiple microsatellite genetic markers were subsequently determined for each response. QTLs were provisionally identified for each phenotype, some unique to a particular behavior and others that appeared to influence multiple phenotypes. Candidate genes suggested by these analyses included several that mapped near genes relevant for the neurotransmitters acetylcholine and glutamate. The locations of QTLs provisionally identified by this analysis were compared with QTLs hypothesized in other studies to influence methamphetamine- and cocaine-related phenotypes. In several instances, QTLs appeared to overlap, which is consistent with idea that common neural substrates underlie some responses to psychostimulants.
Consequences of Nigrostriatal Denervation on the Functioning of the Basal Ganglia in Human and Nonhuman Primates: AnIn SituHybridization Study of Cytochrome Oxidase Subunit I mRNA
Authors: Vila Miquel , Levy Richard , Herrero Maria-Trinidad , Ruberg Merle , Faucheux Baptiste , Obeso José A. , Agid Yves , Hirsch Etienne C.
Published: April 2018

To examine the consequences of nigrostriatal denervation and chronic levodopa (l-DOPA) treatment on functional activity of the basal ganglia, we analyzed, usingin situhybridization, the cellular expression of the mRNA encoding for cytochrome oxidase subunit I (COI mRNA), a molecular marker for functional neuronal activity, in the basal ganglia. This analysis was performed in monkeys rendered parkinsonian by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxication, some of which had been receivingl-DOPA, and in patients with Parkinson’s disease (PD). In MPTP-intoxicated monkeys compared with control animals, COI mRNA expression was increased in the subthalamic nucleus (STN) and in the output nuclei of the basal ganglia, i.e., the internal segment of the globus pallidus and the substantia nigra pars reticulata. This increase was partially reversed byl-DOPA treatment. COI mRNA expression remained unchanged in the external segment of the globus pallidus (GPe). In PD patients, all of whom had been treated chronically byl-DOPA, COI mRNA expression in the analyzed basal ganglia structures was similar to that in control subjects. These results are in agreement with the accepted model of basal ganglia organization, to the extent that the output nuclei of the basal ganglia are considered to be overactive after nigrostriatal denervation, partly because of increased activity of excitatory afferents from the STN. Yet, our results would also seem to contradict this model, because the overactivity of the STN does not seem to be attributable to a hypoactivation of the GPe.
Pontine Nitric Oxide Modulates Acetylcholine Release, Rapid Eye Movement Sleep Generation, and Respiratory Rate
Authors: Leonard Timothy O. , Lydic Ralph
Published: April 2018

Pontine cholinergic neurotransmission is known to play a key role in the regulation of rapid eye movement (REM) sleep and to contribute to state-dependent respiratory depression. Nitric oxide (NO) has been shown to alter the release of acetylcholine (ACh) in a number of brain regions, and previous studies indicate that NO may participate in the modulation of sleep/wake states. The present investigation tested the hypothesis that inhibition of NO synthase (NOS) within the medial pontine reticular formation (mPRF) of the unanesthetized cat would decrease ACh release, inhibit REM sleep, and prevent cholinergically mediated respiratory depression. Local NOS inhibition by microdialysis delivery ofNG-nitro-l-arginine (NLA) significantly reduced ACh release in the cholinergic cell body region of the pedunculopontine tegmental nucleus and in the cholinoceptive mPRF. A second series of experiments demonstrated that mPRF microinjection of NLA significantly reduced the amount of REM sleep and the REM sleep-like state caused by mPRF injection of the acetylcholinesterase inhibitor neostigmine. Duration but not frequency of REM sleep epochs was significantly decreased by mPRF NLA administration. Injection of NLA into the mPRF before neostigmine injection also blocked the ability of neostigmine to decrease respiratory rate during the REM sleep-like state. Taken together, these findings suggest that mPRF NO contributes to the modulation of ACh release, REM sleep, and breathing.
Cellular, Subcellular, and Subsynaptic Distribution of AMPA-Type Glutamate Receptor Subunits in the Neostriatum of the Rat
Authors: Bernard Véronique , Somogyi Peter , Bolam J. Paul
Published: April 2018

Glutamate released in the basal ganglia is involved in the expression of clinical symptoms of neurodegenerative diseases like Parkinson’s or Huntington’s. Neostriatal neurons are the targets of glutamatergic inputs derived from the cortex and the thalamus acting via AMPA-type as well as other glutamate receptors. To determine the location of subunits of the AMPA subclass of glutamate receptors (GluR) in the rat neostriatum, we applied multiple immunocytochemical techniques using anti-peptide antibodies against the GluR1, GluR2/3, and GluR4 subunits at both the light and electron microscopic levels. All medium spiny efferent neurons, some of which were identified as striatonigral neurons, displayed immunoreactivity for GluR1 and GluR2/3 subunits. Double immunofluorescence revealed that at least 70–90% of parvalbumin-immunopositive GABAergic interneurons were immunoreactive for each of GluR1, GluR2/3, or GluR4 subunits and that at least 40% of choline acetyltransferase-immunopositive cholinergic interneurons were immunopositive for GluR1 or GluR4 subunits. The majority of nitric oxide synthase-immunopositive neurons had no detectable immunoreactivity for any of the AMPA receptor subunits. Electron microscopic analysis confirmed the presence of immunoreactivity for GluR1 and GluR2/3 in the perikarya of spiny neurons and interneurons and GluR4 in perikarya of interneurons only. GluR1 and GluR2/3 subunits were detected in dendrites and spines. A significant population of extrasynaptic receptors was revealed by pre-embedding immunogold labeling along the plasma membranes of perikarya, dendrites, and spines. Receptors were concentrated in the postsynaptic membrane specialization of asymmetrical synapses, as revealed by the postembedding immunogold method. Quantitative analysis demonstrated that immunoreactivity for the GluR1 and GluR2/3 subunits is higher at the periphery than at the middle of the postsynaptic membrane specialization.

Our results demonstrate that AMPA receptor subunits are distributed widely and heterogeneously among striatal neurons and are concentrated on the postsynaptic membrane of asymmetrical synaptic specializations, although extrasynaptic receptors are also present.
Differential Localization of δ Glutamate Receptors in the Rat Cerebellum: Coexpression with AMPA Receptors in Parallel Fiber–Spine Synapses and Absence from Climbing Fiber–Spine Synapses
Authors: Landsend Alf Sommer , Amiry-Moghaddam Mahmood , Matsubara Atsushi , Bergersen Linda , Usami Shin-ichi , Wenthold Robert J. , Ottersen Ole P.
Published: April 2018

The δ2 glutamate receptors are prominently expressed in Purkinje cells and are thought to play a key role in the induction of cerebellar long-term depression. The synaptic and subsynaptic localization of δ receptors in rat cerebellar cortex was investigated with sensitive and high-resolution immunogold procedures. After postembedding incubation with an antibody raised to a C-terminal peptide of δ2, high gold particle densities occurred in all parallel fiber synapses with Purkinje cell dendritic spines, whereas other synapses were consistently devoid of labeling. Among the types of immunonegative synapse were climbing fiber synapses with spines and parallel fiber synapses with dendritic stems of interneurons. At the parallel fiber–spine synapse, gold particles signaling δ receptors were restricted to the postsynaptic specialization. By the use of double labeling with two different gold particle sizes, it was shown that δ and AMPA GluR2/3 receptors were colocalized along the entire extent of the postsynaptic specialization without forming separate domains. The distribution of gold particles representing δ receptors was consistent with a cytoplasmic localization of the C terminus and an absence of a significant presynaptic pool of receptor molecules. The present data suggest that the δ2 receptors are targeted selectively to a subset of Purkinje cell spines and that they are coexpressed with ionotropic receptors in the postsynaptic specialization. This arrangement could allow for a direct interaction between the two classes of receptor.
Decreased [18F]Spiperone Binding in Putamen in Idiopathic Focal Dystonia
Authors: Perlmutter Joel S. , Stambuk Mikula K. , Markham Joanne , Black Kevin J. , McGee-Minnich Lori , Jankovic Joseph , Moerlein Stephen M.
Published: April 2018

In this study we have investigated the pathophysiology of two idiopathic focal dystonias: hand cramp with excessive cocontractions of agonist and antagonist hand or forearm muscles during specific tasks, such as writing, and facial dystonia manifested by involuntary eyelid spasms (blepharospasm) and lower facial and jaw spasms (oromandibular dystonia). We used positron emission tomography (PET) to measure thein vivobinding of the dopaminergic radioligand [18F]spiperone in putamen in 21 patients with these two focal dystonias and compared the findings with those from 13 normals. We measured regional cerebral blood flow and blood volume in each subject as well as the radiolabeled metabolites of [18F]spiperone in arterial blood. A stereotactic method of localization, independent of the appearance of the images, was used to identify the putamen in all of the PET images. We analyzed the PET and arterial blood data with a validated nonsteady-state tracer kinetic model representing thein vivobehavior of the radioligand. An index of binding called the combined forward rate constant was decreased by 29% in dystonics, as compared with normals (p< 0.05). There were no significant differences between dystonics and normals in regional blood flow, blood volume, nonspecific binding, permeability–surface area product of [18F]spiperone or the dissociation rate constant. These findings are consistent with a decrease of dopamine D2-like binding in putamen and are the first demonstration of a receptor abnormality in idiopathic dystonia. These results have important implications for the pathophysiology of dystonia as well as for function of the basal ganglia.
Dendritic and Postsynaptic Localizations of Glycine Receptor α Subunit mRNAs
Authors: Racca Claudia , Gardiol Alejandra , Triller Antoine
Published: April 2018

Some synaptic neurotransmitter receptors, such as those for glycine, have somato-dendritic distributions. Although the machinery for protein synthesis and several mRNAs are present in dendrites and close to synapses in central neurons, so far the mRNAs for neurotransmitter receptors have not been found unequivocally in dendrites. The glycine receptor (GlyR), a ligand-gated channel mediating a chloride-dependent inhibition, is composed of transmembrane α and β subunits. GlyRs are only present at glycinergic postsynaptic differentiation, where they are stabilized by the associated protein gephyrin. With light nonradioactivein situhybridization (ISH), we observe that GlyR α subunit mRNAs are present in both somata and dendrites of most neurons of the ventral horn of rat spinal cord, whereas the β subunit and gephyrin mRNAs are predominantly in somata. Interestingly, within dendrites GlyR α subunit mRNAs form aggregates that are mostly localized peripherally to the dendritic axial core. Electron microscopic ISH shows that GlyR α subunit mRNAs are associated with postsynaptic differentiations. At these sites, the GlyR α subunit mRNAs are detected in close association with subsynaptic cisternae. This targeting of α subunit mRNAs to postsynaptic domains could provide a means of dynamically modulating synaptic efficacy by changing the composition and the density of receptors at glycinergic synapses.
Modulation of Oscillator Interactions in the Crab Stomatogastric Ganglion by Crustacean Cardioactive Peptide
Authors: Weimann James M. , Skiebe Petra , Heinzel Hans-Georg , Soto Cristina , Kopell Nancy , Jorge-Rivera Juan Carlos , Marder Eve
Published: April 2018

The modulation of the pyloric rhythm of the stomatogastric ganglion of the crab,Cancer borealis,by crustacean cardioactive peptide (CCAP) is described. CCAP activated pyloric rhythms in most silent preparations, and altered the phase relationships of pyloric motor neuron firing in all preparations. In CCAP, the pyloric rhythms were characterized by long lateral pyloric (LP) neuron bursts of action potentials. The threshold for CCAP action was ∼10−10M, with increasing effects at higher CCAP concentrations. The changes in motor pattern evoked by CCAP produced significant changes in LP-innervated muscle movement. These movements were additionally potentiated by CCAP applications to isolated nerve–muscle preparations. Thus, enhanced motor neuron firing and increase of the gain of the neuromuscular junctions are likely to operate coordinately in response to hormonally released CCAP. High CCAP concentrations sometimes resulted in modification of the normal 1:1 alternation between the pyloric dilator (PD) and LP neurons to patterns of 2:1, 3:1, or 4:1 alternation. CCAP seems to activate slow intrinsic oscillations in the LP neuron, as well as enhance faster oscillations in the pacemaker group of PD/anterior burster (AB) neurons. Simulations of fast and slow oscillators with reciprocal inhibitory coupling suggest mechanisms that could account for the mode switch from 1:1 alternation to multiple PD bursts alternating with one LP neuron burst.
5-HT Inhibits Calcium Current and Synaptic Transmission from Sensory Neurons in Lamprey
Authors: El Manira Abdeljabbar , Zhang Weiqi , Svensson Erik , Bussières Nathalie
Published: April 2018

In the lamprey spinal cord, 5-hydroxytryptamine (5-HT) immunoreactivity (ir) is present in the ventromedial plexus originating from intraspinal neurons, ventrolateral column arising from the brainstem, and dorsal column. The latter 5-HT system originates from small dorsal root ganglion neurons. Combined Lucifer yellow intracellular labeling of the intraspinal sensory neurons, dorsal cells, and 5-HT immunohistochemistry showed close appositions between 5-HT-ir fibers and dorsal cell axons. Application of 5-HT depressed monosynaptic EPSPs evoked in giant interneurons by stimulation of single dorsal cells, dorsal roots, or dorsal column without any detectable change in the input resistance of postsynaptic neurons. Furthermore, the amplitude of AMPA-evoked depolarizations in giant interneurons was unaffected by 5-HT. The lack of postsynaptic effects of 5-HT indicates that the decrease of the amplitude of sensory monosynaptic EPSPs by 5-HT is mediated by presynaptic mechanisms. The inhibition of monosynaptic EPSPs by 5-HT was not counteracted by an antagonist of 5-HT1Areceptors. 5-HT also reduced the amplitude of the calcium current recorded in isolated dorsal cells and slowed down its kinetics. The inhibition of calcium channels could represent the mechanism mediating the depression of synaptic transmission at the axonal level. These results show that activation of 5-HT receptors on dorsal cell axons as well as on other sensory neurons mediates inhibition of sensory synaptic transmission to giant interneurons. In intact animals, 5-HT could be released from small 5-HT neurons in dorsal root ganglia, which thus may underlie direct sensory–sensory interactions.
Selective Roles for Hippocampal, Prefrontal Cortical, and Ventral Striatal Circuits in Radial-Arm Maze Tasks With or Without a Delay
Authors: Floresco Stan B. , Seamans Jeremy K. , Phillips Anthony G.
Published: April 2018

The hippocampus, the prefrontal cortex, and the ventral striatum form interconnected neural circuits that may underlie aspects of spatial cognition and memory. In the present series of experiments, we investigated functional interactions between these areas in rats during the performance of delayed and nondelayed spatially cued radial-arm maze tasks. The two-phase delayed task consisted of a training phase that provided rats with information about where food would be located on the maze 30 min later during a test phase. The single-phase nondelayed task was identical to the test phase of the delayed task, but in the absence of a training phase rats lacked previous knowledge of the location of food on the maze. Transient inactivation of the ventral CA1/subiculum (vSub) by a bilateral injection of lidocaine disrupted performance on both tasks. Lidocaine injections into the vSub on one side of the brain and the prefrontal cortex on the other transiently disconnected these two brain regions and significantly impaired foraging during the delayed task but not the nondelayed task. Transient disconnections between the vSub and the nucleus accumbens produced the opposite effect, disrupting foraging during the nondelayed task but not during the delayed task. These data suggest that serial transmission of information between the vSub and the prefrontal cortex is required when trial-unique, short-term memory is used to guide prospective search behavior. In contrast, exploratory goal-directed locomotion in a novel situation not requiring previously acquired information about the location of food is dependent on serial transmission between the hippocampus and the nucleus accumbens. These results indicate that different aspects of spatially mediated behavior are subserved by separate, distributed limbic–cortical–striatal networks.
Nedd2 Is Required for Apoptosis after Trophic Factor Withdrawal, But Not Superoxide Dismutase (SOD1) Downregulation, in Sympathetic Neurons and PC12 Cells
Authors: Troy Carol M. , Stefanis Leonidas , Greene Lloyd A. , Shelanski Michael L.
Published: April 2018

Activation of cysteine aspartases (caspases) seems to be a required element of apoptotic death in many paradigms. We have shown previously that general inhibitors of cysteine aspartases block apoptosis of PC12 cells and sympathetic neurons evoked by either trophic factor (nerve growth factor and/or serum) deprivation or superoxide dismutase (SOD1) downregulation. Moreover, activation of a caspase family member similar or equivalent to the interleukin-1β-converting enzyme (ICE) was implicated for death caused by SOD1 downregulation, but not withdrawal of trophic support. The experiments presented here demonstrate that diminished expression of the cysteine aspartase Nedd2 in PC12 cells and sympathetic neurons induced by an appropriate vector peptide-linked antisense oligonucleotide rescues them from death caused by trophic factor deprivation without inhibiting apoptosis in the same cell types evoked by SOD1 downregulation. Neither the level (as revealed by Western immunoblotting) nor the cellular distribution (as revealed immunohistochemically) of Nedd2 was altered demonstrably by trophic factor deprivation. However, evidence for proteolytic processing of Nedd2 (consistent with commencement of activation) was observed in PC12 cells after withdrawal of trophic support. These findings indicate that neuronal death triggered by different initial causes may be mediated by distinct members of the cysteine aspartase family.
Light and Electron Microscopic Localization of Presenilin-1 in Primate Brain
Authors: Lah James J. , Heilman Craig J. , Nash Norman R. , Rees Howard D. , Yi Hong , Counts Scott E. , Levey Allan I.
Published: April 2018

Several genes have been implicated in the pathogenesis of early-onset familial Alzheimer’s disease. A majority of the autosomal dominant cases are linked to recently identified mutations in the presenilin-1 gene on chromosome 14. The native presenilin-1 protein in primates has not been well characterized, and its precise localization is unknown. We have studied the native presenilin-1 protein in monkey brain and peripheral tissues by using a monoclonal antibody specific for the N-terminal domain of human presenilin-1. Western blots detect polypeptide species of ∼49 and ∼32 kDa from COS-7 and PC12 cells transfected with full-length human presenilin-1 cDNA and fromin vitrotranslations of the normal human presenilin-1 mRNA. A 32 kDa polypeptide is detected in monkey peripheral tissues, with the highest expression in testis and lung. In all brain regions the 32 kDa band is the predominant form of presenilin-1, and it is found in particulate subfractions. Light microscopic immunocytochemistry reveals presenilin-1 staining in all brain regions, with the strongest labeling in neurons and neuropil. In addition, weaker immunoreactivity is also present in glia and blood vessels. Neuronal staining shows significant variability, with particularly intense labeling of certain cell types, including large neocortical and hippocampal pyramidal neurons, magnocellular basal forebrain neurons, brainstem motoneurons, and some populations of interneurons. By electron microscopic immunocytochemistry, highly selective presenilin-1 staining is seen on the cytoplasmic surfaces of membranous organelles, which suggest localization to the endoplasmic reticulum–Golgi intermediate compartment, a subdomain of the endoplasmic reticulum, and some coated transport vesicles.
Neurotrophins Suppress Apoptosis Induced by Deafferentation of an Avian Motor-Cortical Region
Authors: Johnson Frank , Hohmann Stephen E. , DiStefano Peter S. , Bottjer Sarah W.
Published: April 2018

Studies of the developing nervous system led to the general view that growth factors promote neuronal survival in a “retrograde” manner. For example, release of NGF from postsynaptic peripheral targets followed by uptake and retrograde transport by presynaptic neurons provided a widely accepted conceptual framework for the action of neurotrophins. In contrast, although presynaptic or “anterograde” influences on the survival of developing neurons have been recognized for some time, the mechanisms by which afferent input regulates the survival of postsynaptic cells have received considerably less attention. In the forebrain network for learned vocal behavior in zebra finches, lesions of a cortical region for song control, the lateral magnocellular nucleus of the anterior neostriatum (lMAN), remove presynaptic input to a motor-cortical song region, the robust nucleus of the archistriatum (RA), and cause massive RA neuron death in young birds that are entering the sensitive period for song learning. Here we report that lesions of lMAN followed by infusions of neurotrophins directly into RA completely suppress neuronal apoptosis in RA. Moreover, we show that lMAN neurons are able to transport neurotrophins in the anterograde direction to RA, that neurotrophin-like immunoreactivity is present in cells in lMAN and RA, and that neurotrophin receptor-like immunoreactivity is present in RA. Expression of neurotrophins in lMAN and RA suggests that lMAN presynaptic input could regulate RA neuron survival by synthesizing, transporting, and releasing neurotrophins anterogradely or by regulating the auto/paracrine release of neurotrophins within RA, or perhaps by both. These data provide the firstin vivodemonstration that neurotrophins can prevent the death of deafferented cortical neurons, and they raise the possibility that nonretrograde signaling by neurotrophins may be a common means of promoting neuronal survival in the vertebrate telencephalon. Anterograde and auto/paracrine neurotrophin signaling, along with the more established view that neurotrophins regulate neuron survival via retrograde mechanisms, suggests multidirectional neurotrophin signaling in the vertebrate telencephalon.