bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiple Subtypes of Voltage-Gated Calcium Channel Mediate Transmitter Release from Parasympathetic Neurons in the Mouse Bladder
Authors: Waterman Sally A. 
Published: April 2018

Multiple subtypes of voltage-gated calcium channels are coupled to transmitter release from central neurons; however, only N-type channels have been shown to play a role in autonomic neurons. The aim of the present study was to investigate potential roles for other channel subtypes in transmitter release from parasympathetic neurons in the mouse bladder using calcium channel toxins alone and in combination. Transmitter release was measured indirectly by recording the contraction of bladder dome strips in response to electrical stimulation of the neurons by single pulses or trains of 20 pulses at 1–50 Hz. ω-Conotoxin-GVIA (GVIA) and ω-conotoxin-MVIIC (MVIIC) inhibited contractions in a concentration-dependent manner, with IC50values of ∼30 and 200 nm, respectively, at low stimulation frequencies. ω-Agatoxin-IVA (agatoxin) alone did not have any significant effect up to 300 nm. Cumulative addition of the toxins demonstrated that 300 nmagatoxin had a significant effect after N-type channels were blocked with 100 nmGVIA. MVIIC (3 μm) reduced the contraction amplitude further. Testing the toxins on the cholinergic or purinergic component of the contraction separately showed that acetylcholine release depends primarily on N-type channels and, to a lesser extent, on P- and Q-type channels, whereas ATP release involves predominantly P- and Q-type channels. In conclusion, parasympathetic neurons in the mouse bladder, like central neurons, use multiple calcium channel subtypes. Furthermore, the release of the two main transmitters in these neurons has differing dependencies on the calcium channel subtypes.
Protection of Retinal Ganglion Cells from Natural and Axotomy-Induced Cell Death in Neonatal Transgenic Mice Overexpressing bcl-2
Authors: Bonfanti Lidia , Strettoi Enrica , Chierzi Sabrina , Cenni Maria Cristina , Liu Xiu-Huai , Martinou Jean-Claude , Maffei Lamberto , Rabacchi Sylvia A. 
Published: April 2018

Approximately half of the retinal ganglion cells (RGCs) present in the rodent retina at birth normally die during early development. Overexpression of the proto-oncogene bcl-2 recently has been shown to rescue some neuronal populations from natural cell death and from degeneration induced by axotomy of nerves within the peripheral nervous system. Here we studyin vivothe role of the overexpression of bcl-2 in the natural cell death of RGCs and in the degenerative process induced in these cells by transection of the optic nerve. We find that in newborn bcl-2 transgenic mice, the number of RGCs undergoing natural cell death is considerably lower than in wild-type pups. Consistently, a vast majority (90%) of the ganglion cells found in the retina of neonatal transgenics are maintained in adulthood, whereas only 40% survive in wild-type mice.After transection of the optic nerve, the number of degenerating ganglion cells, determined by counting pyknotic nuclei or nuclei with fragmented DNA, is substantially reduced in transgenic mice. In wild-type animals, almost 50% of ganglion cells degenerate in the 24 hr after the lesion, whereas almost the entire ganglion cell population survives axotomy in transgenic mice. Therefore, overexpression of bcl-2 is effective in preventing degeneration of this neuronal population, raising the possibility that ganglion cells are dependent on the endogenous expression of bcl-2 for survival. The remarkable rescue capacity of bcl-2 overexpression in these neurons makes it an interesting model for studying natural cell death and responses to injury in the CNS.
Dual Action of a Carbohydrate Epitope on Afferent and Efferent Axons in Cortical Development
Authors: Henke-Fahle Sigrid , Mann Fanny , Götz Magdalena , Wild Karen , Bolz Jürgen 
Published: April 2018

During development of the mammalian cerebral cortex, ingrowing afferents from the thalamus take a path that is different from that of axons leaving the cortical plate. Thalamic axons arrive at the cortex at the time before their target cells of layer 4 are generated in the ventricular zone, but they invade the cortex only shortly before these cells have migrated to their final position in the cortex. Growth-promoting molecules are upregulated in the developing cortical plate during this period. To identify such molecules, we have generated monoclonal antibodies against membrane preparations from rat postnatal cortex. In Western blots, one antibody (mAb 10) recognized a carbohydrate epitope of a glycoprotein with an apparent molecular weight extending from 180 to 370 kDa. Immunohistochemical staining revealed that the staining pattern of mAb 10 at embryonic stages delineates the pathway of thalamocortical axons, with only very faint labeling of the corticofugal pathway.In vitroassays in combination with time-lapse imaging indicated that mAb 10 has opposite effects on the growth of thalamic and cortical axons. The growth speed and axonal elongation of thalamic fibers on postnatal cortical membranes preincubated with mAb 10 was reduced compared with untreated cortical membranes. In contrast, cortical axons grew faster and stopped their growth less frequently after addition of mAb 10 to a cortical membrane substrate. Taken together, these results suggest that a carbohydrate moiety of a membrane-associated glycoprotein plays a role in the segregation of afferent and efferent cortical axons in the white matter. Moreover, the epitope recognized by mAb 10 might also contribute to regulation of the timing of the thalamocortical innervation at later developmental stages.
Kainic Acid-Induced Seizures Enhance Dentate Gyrus Inhibition by Downregulation of GABABReceptors
Authors: Haas Kurt Z. , Sperber Ellen F. , Moshé Solomon L. , Stanton Patric K. 
Published: April 2018

Seizures cause a persistent enhancement in dentate synaptic inhibition concurrent with, and possibly compensatory for, seizure-induced hippocampal hyperexcitability. To study this phenomenon, we evoked status epilepticus in rats with systemic kainic acid (KA), and 2 weeks later assessed granule cell inhibition with paired-pulse stimulation of the perforant path (PP)in vitro. Controls demonstrated three components of paired-pulse inhibition: early inhibition (10–30 msec), intermediate facilitation (30–120 msec), and late inhibition (120 msec to 120 sec). After seizures, inhibition in all components was enhanced significantly. The GABAAantagonist bicuculline blocked only early enhanced inhibition, demonstrating that both GABAAand GABABpostsynaptic receptors contribute to seizure-induced enhanced inhibition. In controls, the GABABantagonist CGP 35348 increased both GABAAand GABABresponses in granule cells, suggesting that CGP 35348 acts presynaptically, blocking receptors that suppress GABA release. In contrast, slices from KA-treated rats were markedly less sensitive to CGP 35348. To test the hypothesis that GABABreceptors regulating GABA release are downregulated after seizures, we measured paired-pulse suppression of recurrent IPSPs, or disinhibition, using mossy fiber stimuli. Early disinhibition (< 200 msec) was reduced after seizures, whereas late disinhibition remained intact. CGP 35348 blocked the early component of disinhibition in controls and, to a lesser extent, reduced disinhibition in KA slices. However, paired monosynaptic IPSPs recorded intracellularly showed no difference in disinhibition between groups. Our findings indicate that seizure-induced enhancement in dentate inhibition is caused, at least in part, by reduced GABABfunction in the polysynaptic recurrent inhibitory circuit, resulting in reduced disinhibition and heightened GABA release.
Cerebral Representation of One’s Own Past: Neural Networks Involved in Autobiographical Memory
Authors: Fink Gereon R. , Markowitsch Hans J. , Reinkemeier Mechthild , Bruckbauer Thomas , Kessler Josef , Heiss Wolf-Dieter 
Published: April 2018

We studied the functional anatomy of affect-laden autobiographical memory in normal volunteers. Using H215O positron emission tomography (PET), we measured changes in relative regional cerebral blood flow (rCBF). Four rCBF measurements were obtained during three conditions: REST, i.e., subjects lay at rest (for control); IMPERSONAL, i.e., subjects listened to sentences containing episodic information taken from an autobiography of a person they did not know, but which had been presented to them before PET scanning (nonautobiographical episodic memory ecphory); and PERSONAL, i.e., subjects listened to sentences containing information taken from their own past (autobiographical episodic memory ecphory).Comparing IMPERSONAL with REST (nonautobiographical episodic memory ecphory) resulted in relative rCBF increases symmetrically in both temporal lobes including the temporal poles and medial and superior temporal gyri. The same loci, however, with a stronger lateralization to the right hemisphere were activated in the comparison PERSONAL to REST (autobiographical episodic memory ecphory). In addition, the right temporomesial, right dorsal prefrontal, right posterior cingulate areas, and the left cerebellum were activated. A comparison of PERSONAL and IMPERSONAL (autobiographical vs nonautobiographical episodic memory ecphory) demonstrated a preponderantly right hemispheric activation including primarily right temporomesial and temporolateral cortex, right posterior cingulate areas, right insula, and right prefrontal areas. The right temporomesial activation included hippocampus, parahippocampus, and amygdala.These results suggest that a right hemispheric network of temporal, together with posterior, cingulate, and prefrontal, areas is engaged in the ecphory of affect-laden autobiographical information.
Phenotypic Alteration of a Human BK (hSlo) Channel byhSloβSubunit Coexpression: Changes in Blocker Sensitivity, Activation/Relaxation and Inactivation Kinetics, and Protein Kinase A Modulation
Authors: Dworetzky Steven I. , Boissard Christopher G. , Lum-Ragan Janet T. , McKay M. Craig , Post-Munson Debra J. , Trojnacki Joanne T. , Chang Chia-Ping , Gribkoff Valentin K. 
Published: April 2018

A human homolog of the large-conductance calcium-activated potassium (BK) channel β subunit (hSloβ) was cloned, and its effects on a human BK channel (hSlo) phenotype are reported. Coexpression ofhSloandhSloβ, in both oocytes and human embryonic kidney 293 cells, resulted in increased Ca2+sensitivity, marked slowing of BK channel activation and relaxation, and a significant reduction in slow inactivation. In addition, coexpression changed the pharmacology of the BK channel phenotype:hSlo-mediated currents in oocytes were more sensitive to the peptide toxin iberiotoxin than werehSlo + hSloβ currents, and the potency of blockade by the alkaloid BK blocker tetrandrine was much greater onhSlo + hSloβ-mediated currents compared withhSlocurrents alone. No significant differences in the response to charybdotoxin or the BK channel opener NS1619 were observed. Modulation of BK channel activity by phosphorylation was also affected by the presence of thehSloβ subunit. Application of cAMP-dependent protein kinase increasedPOPENofhSlochannels, but decreasedPOPENof mosthSlo + hSloβ channels. Taken together, these altered characteristics may explain some of the wide diversity of BK channel phenotypes observed in native tissues.
Involvement of a Phorbol Ester-Insensitive Protein Kinase C in the α2-Adrenergic Inhibition of Voltage-Gated Calcium Current in Chick Sympathetic Neurons
Authors: Boehm Stefan , Huck Sigismund , Freissmuth Michael 
Published: April 2018

α2-Adrenoceptors regulate the efficacy at the sympatho-effector junction by means of a feedback inhibition of transmitter release. In chick sympathetic neurons, the mechanism involves an inhibition of N-type calcium channels, and we now present evidence that this effect involves an atypical, phorbol ester-insensitive protein kinase C (PKC). The inhibition of voltage-gated Ca2+currents by the specific α2-adrenergic agonist UK 14,304 was significantly attenuated when the PKC inhibitors PKCI(19–36), staurosporine, or calphostin C were included in the internal solution used to fill the patch pipettes, or if staurosporine or calphostin C were applied extracellularly; however, phorbol esters as classical activators of PKC or oleoylacetylglycerol did not mimic the effect of UK 14,304, and chronic exposure to 4-β-phorbol dibutyrate (PDBu) did not attenuate it, even though PKCα and -ε isozymes were translocated to plasma membranes by PDBu. The atypical isozyme PKCζ was translocated by 100 μmarachidonic acid (AA), but not by PDBu; 100 μmAA and linoleic acid inhibited voltage-activated Ca2+currents, and this effect was attenuated when PKCI(19–36) was added to the patch pipette solution. Our observations indicate that classical, new, and atypical PKC isozymes are present in chick sympathetic neurons and that an atypical, phorbol ester-insensitive PKC is involved in the inhibition of voltage-activated calcium currents by α2-adrenoceptor activation.
Selective G-Protein Regulation of Neuronal Calcium Channels
Authors: Toth Peter T. , Shekter Lee R. , Hui Ma Gloria , Philipson Louis H. , Miller Richard J. 
Published: April 2018

We examined the properties and regulation of Ca channels resulting from the expression of human α1Band α1Esubunits stably expressed in HEK293 cells. The ancillary subunits β1Band α2/δ were also stably expressed in these cell lines. Ca currents in α1B-expressing cells had the properties of N-type currents. Ca currents in cells expressing α1Eexhibited a novel profile that was similar to the properties of the “R type” Ca current. Introduction of GTP-γ-S into α1Bcells greatly enhanced the extent of prepulse facilitation of the Ca current, whereas it had only a very small effect in α1E-expressing cells. Activation of somatostatin receptors endogenous to HEK293 cells or κ opioid receptors, expressed in the cells after transfection, inhibited Ca currents in α1B-expressing cells. This inhibition was blocked by pertussis toxin and was partially relieved by a depolarizing prepulse. In contrast, no inhibitory effects were noted in cells expressing α1Echannels under the same circumstances. HEK293 cells normally contained G-proteins from all of the four major families. Inhibition of Ca currents by κ agonists in α1B-expressing cells was enhanced slightly by the cotransfection of several G-protein α subunits. κ agonists, however, had no effect in α1E-containing cells, even after overexpression of different G-protein α-subunits. In summary, these results demonstrate that there is a large difference in the susceptibility of α1B- and α1E-based Ca channels to regulation by G-proteins. This is so despite the fact that the two types of Ca channels show substantial similarities in their primary sequences.
Electrophysiological Characterization of Chemosensory Neurons from the Mouse Vomeronasal Organ
Authors: Liman Emily R. , Corey David P. 
Published: April 2018

The mechanism of sensory transduction in chemosensory neurons of the vomeronasal organ (VNO) is not known. Based on molecular data, it is likely to be different from that mediating sensory transduction in the main olfactory system. To begin to understand this system, we have characterized the electrophysiological properties of dissociated mouse VNO neurons with patch-clamp recording. Sensory neurons were distinguished from nonsensory neurons by the presence of a dendrite, by immunoreactivity for olfactory marker protein, and by the firing of action potentials. The resting potential of VNO neurons was approximately −60 mV, and the average input resistance was 3 GΩ. Current injections as small as 1–2 pA elicited steady trains of action potentials that showed no sign of adaptation during a 2 sec stimulus duration. The voltage-gated conductances in VNO neurons are distinct from those in olfactory neurons. The Na+current is composed of two components; the major component was TTX-sensitive (Ki = 3.6 nm). The outward K+current activates at −30 mV with kinetics 10 times slower than for K+currents in olfactory neurons. The Ca2+current is composed of at least two components: an L-type current and a T-type current that activates at −60 mV and is not found in olfactory neurons. We find no evidence for cyclic nucleotide-gated channels in VNO neurons under a variety of experimental conditions, including those that produced large responses in mouse olfactory neurons, which is further evidence for a novel transduction pathway.
Glial Growth Factor 2, a Soluble Neuregulin, Directly Increases Schwann Cell Motility and Indirectly Promotes Neurite Outgrowth
Authors: Mahanthappa Nagesh K. , Anton Eva S. , Matthew William D. 
Published: April 2018

Schwann cells proliferate, migrate, and act as sources of neurotrophic support during development and regeneration of peripheral nerves. Recent studies have demonstrated that neuregulins, a family of growth factors secreted by developing motor and peripheral neurons, influence Schwann cell development. In this study, we use three distinct assays to show that glial growth factor 2 (GGF2), a secreted neuregulin, exerts multiple effects on mature Schwann cellsin vitro. At doses submaximal for proliferation, GGF2 increases the motility of Schwann cells cultured on peripheral nerve cryosections. Furthermore, in a novel bioassay, focal application of GGF2 causes directed migration in conventional monolayer cultures of Schwann cells. At higher doses, GGF2 causes proliferation, as described previously. In a new explant culture system designed to emulate entubulation repair of transected peripheral nerves, GGF2 concentrations greater than necessary to saturate the mitotic response induce the secretion by Schwann cells of activities that promote sympathetic neuron survival and outgrowth. These findings support a model in which neuregulins secreted by peripheral neurons are key components of reciprocal neuron–glia interactions that are important for peripheral nerve development and regeneration.
Comparative Study of Pre- and Postsynaptic 5-HT1AReceptor Modulation of Anxiety in Two Ethological Animal Tests
Authors: File Sandra E. , Gonzalez Luis E. , Andrews Nick 
Published: April 2018

The purpose of this study was to determine the roles of the presynaptic 5-hydroxytryptamine1A(5-HT1A) receptors in the median raphénucleus (MRN) and of the postsynaptic 5-HT1Areceptors in its projection area of the dorsal hippocampus in the social interaction and elevated plus-maze tests of anxiety. Direct administration of the 5-HT1Areceptor agonist (±)-8-hydroxy-dipropylaminotetralin (8-OH-DPAT, 200 ng) into the MRN had significant anxiolytic effects in all three test situations examined (social interaction, plus-maze trials 1 and 2). These anxiolytic effects were antagonized by a silent dose (200 ng) of the 5-HT1Areceptor antagonist WAY 100635, confirming that they were mediated by 5-HT1Areceptors. In contrast, after bilateral administration to the dorsal hippocampus, 8-OH-DPAT (100 ng) had significant anxiogenic effects in the social interaction test and in plus-maze trial 2. These anxiogenic effects were antagonized by silent doses of 5-HT1Areceptor antagonists [(+)WAY 100135, 10 mg/kg s.c., and intrahippocampal (±)tertatolol, 3 μg, respectively], confirming mediation by 5-HT1Areceptors. In rats naive to the plus-maze, neither 8-OH-DPAT (50, 100, or 200 ng) nor the 5-HT1Areceptor antagonist (±)tertatolol (3 μg) had any significant effect when administered to the dorsal hippocampus. This demonstrates that previous experience of a rat in the plus-maze has a major effect on the sensitivity of dorsal hippocampal 5-HT1Areceptors, as we have demonstrated previously for the 5-HT1Areceptors in the dorsal raphé nucleus. Overall, our results provide evidence that stimulation of the presynaptic 5-HT1Areceptors in the MRN results in an anxiolytic action, whereas stimulation of the post-synaptic 5-HT1Areceptors in its projection area results in an anxiogenic effect. These results are consistent with an overall reduction in 5-HT neurotransmission in the dorsal hippocampus having an anxiolytic effect, and they explain the relatively weak anxiolytic profile detected when 5-HT1Areceptor agonists are given systemically.
Functional Diversity of P-Type and R-Type Calcium Channels in Rat Cerebellar Neurons
Authors: Tottene Angelita , Moretti Alessandra , Pietrobon Daniela 
Published: April 2018

By combining single-channel and whole-cell patch-clamp recordings, we have established the sensitivity to ω-agatoxin IVA and ω-conotoxin MVIIC (SNX-230) of G1, G2, and G3, the three novel non-L-, non-N-type Ca2+channels characterized previously in rat cerebellar granule cells. G1 channels were blocked irreversibly by both ω-conotoxin MVIIC and low doses of ω-agatoxin IVA (saturation at 50 nm). Thus, according to pharmacological criteria, G1 channels must be classified as P-type Ca2+channels. Being slowly inactivating during depolarizing pulses and completely inactivated at voltages in which steady-state inactivation of P-type channels in Purkinje cells is negligible, G1 represents a novel P subtype. Neither G2 nor G3 was blocked irreversibly by ω-conotoxin MVIIC, and therefore both are R-type Ca2+channels. G2 and G3 have some biophysical properties similar to those of low-voltage-activated (LVA) Ca2+channels (e.g., voltage range for steady-state inactivation,V1/2 = −90 mV), some properties similar to those of high-voltage-activated (HVA) Ca2+channels (e.g., high sensitivity to Cd2+block), and other properties intermediate between those of LVA and HVA Ca2+channels, with LVA properties prevailing in G2 and HVA properties prevailing in G3. The R-type whole-cell current was inhibited by Ni2+with a biphasic dose–response curve (IC50: 4 and 153 μm), suggesting that G2 and G3 may have a different sensitivity to Ni2+block. Our results uncover functional diversity of both native P-type and R-type Ca2+channels and show that R subtypes with distinct biophysical properties are coexpressed in rat cerebellar granule cells.
GABABReceptor-Activated Inwardly Rectifying Potassium Current in Dissociated Hippocampal CA3 Neurons
Authors: Sodickson Deborah L. , Bean Bruce P. 
Published: April 2018

GABA and the GABABreceptor agonist baclofen activated a potassium conductance in acutely dissociated hippocampal CA3 neurons. Baclofen-activated current required internal GTP, was purely potassium selective, and showed strong inward rectification. As with acetylcholine-activated current in atrial myocytes, external Cs+blocked inward but not outward current in a highly voltage-dependent manner, whereas Ba2+blocked with no voltage dependence. Unlike the cardiac current, however, the baclofen-activated current showed no intrinsic voltage-dependent relaxation. With fast solution exchange, current was activated by baclofen or GABA with a lag of ∼50 msec followed by an exponential phase (time constant ∼225 msec at saturating agonist concentrations); deactivation was preceded by a lag of ∼150 msec and occurred with a time constant of ∼1 sec. GABA activated the potassium conductance with a half maximally effective concentration (EC50) of 1.6 μm, much lower than that for activation of GABAAreceptor-activated chloride current in the same cells (EC50∼25 μm). At low GABA concentrations, activation of the GABABcurrent had a Hill coefficient of 1.4–2.1, suggesting cooperativity in the receptor-to-channel pathway. Although the maximal conductance activated by GABABreceptors is much smaller than that activated by GABAAreceptors, its higher sensitivity to GABA and slower time course make it well suited to respond to low concentrations of extra-synaptic GABA.