A reinforcing circuit action of extrasynaptic GABAA receptor modulators on cerebellar granule cell inhibition.

GABAA receptors (GABARs) are the targets of a wide variety of modulatory drugs which enhance chloride flux through GABAR ion channels. Certain GABAR modulators appear to acutely enhance the function of δ subunit-containing GABAR subtypes responsible for tonic forms of inhibition. Here we identify a reinforcing circuit mechanism by which these drugs, in addition to directly enhancing GABAR function, also increase GABA release. Electrophysiological recordings in cerebellar slices from rats homozygous for the ethanol-hypersensitive (α6100Q) allele show that modulators and agonists selective for δ-containing GABARs such as THDOC, ethanol and THIP (gaboxadol) increased the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) in granule cells. Ethanol fails to augment granule cell sIPSC frequency in the presence of glutamate receptor antagonists, indicating that circuit mechanisms involving granule cell output contribute to ethanol-enhancement of synaptic inhibition. Additionally, GABAR antagonists decrease ethanol-induced enhancement of Golgi cell firing. Consistent with a role for glutamatergic inputs, THIP-induced increases in Golgi cell firing are abolished by glutamate receptor antagonists. Moreover, THIP enhances the frequency of spontaneous excitatory postsynaptic currents in Golgi cells. Analyses of knockout mice indicate that δ subunit-containing GABARs are required for enhancing GABA release in the presence of ethanol and THIP. The limited expression of the GABAR δ subunit protein within the cerebellar cortex suggests that an indirect, circuit mechanism is responsible for stimulating Golgi cell GABA release by drugs selective for extrasynaptic isoforms of GABARs. Such circuit effects reinforce direct actions of these positive modulators on tonic GABAergic inhibition and are likely to contribute to the potent effect of these compounds as nervous system depressants

The Implications of Animal Research for Problems in Mental Health

The title of this talk is stated in a much too positive way for one to feel fully comfortable about it. Perhaps it should end with a question mark rather than a period. That is, it appears legitimate to ask: what sorts of implications, if any, does animal research have for mental health? The simplest and most honest answer (assuming that we all know what the term mental health means, in the first place) is that we don\u27t know

Changes in Purkinje cell firing and gene expression precede behavioral pathology in a mouse model of SCA2.

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominantly inherited disorder, which is caused by a pathological expansion of a polyglutamine (polyQ) tract in the coding region of the ATXN2 gene. Like other ataxias, SCA2 most overtly affects Purkinje cells (PCs) in the cerebellum. Using a transgenic mouse model expressing a full-length ATXN2(Q127)-complementary DNA under control of the Pcp2 promoter (a PC-specific promoter), we examined the time course of behavioral, morphologic, biochemical and physiological changes with particular attention to PC firing in the cerebellar slice. Although motor performance began to deteriorate at 8 weeks of age, reductions in PC number were not seen until after 12 weeks. Decreases in the PC firing frequency first showed at 6 weeks and paralleled deterioration of motor performance with progression of disease. Transcription changes in several PC-specific genes such as Calb1 and Pcp2 mirrored the time course of changes in PC physiology with calbindin-28 K changes showing the first small, but significant decreases at 4 weeks. These results emphasize that in this model of SCA2, physiological and behavioral phenotypes precede morphological changes by several weeks and provide a rationale for future studies examining the effects of restoration of firing frequency on motor function and prevention of future loss of PCs

Isolation of Current Components and Partial Reaction Cycles in the Glial Glutamate Transporter EAAT2

The kinetic properties of the excitatory amino acid transporter EAAT2 were studied using rapid applications of l-glutamate to outside-out patches excised from transfected human embryonic kidney 293 cells. In the presence of the highly permeant anion SCN−, pulses of glutamate rapidly activated transient anion channel currents mediated by the transporter. In the presence of the impermeant anion gluconate, glutamate pulses activated smaller currents predicted to result from stoichiometric flux of cotransported ions. Both anion and stoichiometric currents displayed similar kinetics, suggesting that anion channel gating and stoichiometric charge movements are linked to early transitions in the transport cycle. Transporter-mediated anion currents were recorded with ion and glutamate gradients favoring either unidirectional influx or exchange. Analysis of deactivation and recovery kinetics in these two conditions suggests that, after binding, translocation of substrate is more likely than unbinding under physiological conditions. The kinetic properties of EAAT2, the dominant glutamate transporter in brain astrocytes, distinguish it as an efficient sink for synaptically released glutamate

DARPA

Issued as Progress reports no. [1-3], Project no. E-25-64

A positive feedback loop linking enhanced mGluR function and basal calcium in spinocerebellar ataxia type 2

Metabotropic glutamate receptor 1 (mGluR1) function in Purkinje neurons (PNs) is essential for cerebellar development and for motor learning and altered mGluR1 signaling causes ataxia. Downstream of mGluR1, dysregulation of calcium homeostasis has been hypothesized as a key pathological event in genetic forms of ataxia but the underlying mechanisms remain unclear. We find in a spinocerebellar ataxia type 2 (SCA2) mouse model that calcium homeostasis in PNs is disturbed across a broad range of physiological conditions. At parallel fiber synapses, mGluR1-mediated excitatory postsynaptic currents (EPSCs) and associated calcium transients are increased and prolonged in SCA2 PNs. In SCA2 PNs, enhanced mGluR1 function is prevented by buffering [Ca 2+ ] at normal resting levels while in wildtype PNs mGluR1 EPSCs are enhanced by elevated [Ca 2+ ]. These findings demonstrate a deleterious positive feedback loop involving elevated intracellular calcium and enhanced mGluR1 function, a mechanism likely to contribute to PN dysfunction and loss in SCA2

Robust photoregulation of GABA(A) receptors by allosteric modulation with a propofol analogue.

Photochemical switches represent a powerful method for improving pharmacological therapies and controlling cellular physiology. Here we report the photoregulation of GABA(A) receptors (GABA(A)Rs) by a derivative of propofol (2,6-diisopropylphenol), a GABA(A)R allosteric modulator, which we have modified to contain photoisomerizable azobenzene. Using α(1)β(2)γ(2) GABA(A)Rs expressed in Xenopus laevis oocytes and native GABA(A)Rs of isolated retinal ganglion cells, we show that the trans-azobenzene isomer of the new compound (trans-MPC088), generated by visible light (wavelengths ~440 nm), potentiates the γ-aminobutyric acid-elicited response and, at higher concentrations, directly activates the receptors. cis-MPC088, generated from trans-MPC088 by ultraviolet light (~365 nm), produces little, if any, receptor potentiation/activation. In cerebellar slices, MPC088 co-applied with γ-aminobutyric acid affords bidirectional photomodulation of Purkinje cell membrane current and spike-firing rate. The findings demonstrate photocontrol of GABA(A)Rs by an allosteric ligand, and open new avenues for fundamental and clinically oriented research on GABA(A)Rs, a major class of neurotransmitter receptors in the central nervous system

Cognitive behavioral therapy for the management of multiple sclerosis–related pain: a randomized clinical trial

BACKGROUND: Pain is a common and often debilitating symptom among persons with multiple sclerosis (PwMS). Besides interfering with daily functioning, pain in MS is associated with higher levels of depression and anxiety. While cognitive-behavioral therapy (CBT) for pain has been found to be an effective treatment in other populations, there has been a dearth of research in PwMS. METHODS: PwMS with at least moderate pain severity (N = 20) were randomly assigned to one of two groups: CBT plus standard care (CBT/SC) or MS-related education plus standard care (ED/SC), each of which met for 12 sessions. Changes in pain severity, pain interference, and depressive symptom severity from baseline to the 15 week follow-up were assessed using a 2×2 factorial design. Participants also rated their satisfaction with their treatment and accomplishment of personally meaningful behavioral goals. RESULTS: Both treatment groups rated their treatment satisfaction as very high and their behavioral goals as largely met, although only the CBT/SC group's mean goal accomplishment ratings represented significant improvement. While there were no significant differences between groups post-treatment on the three primary outcomes, there was an overall improvement over time for pain severity, pain interference, and depressive symptom severity. CONCLUSIONS: CBT or education-based programs may be helpful adjunctive treatments for PwMS experiencing pain.Accepted manuscrip

Identification of Walleye X Sauger Hybrid By Isozyme Electrophoresis

Of 125 phenotypic walleye screened by isozyme electrophoresis, one unusual individual was detected and subsequently suspected of being a walleye (Stizostedion vitreum vitreum) x sauger (S. canadense) hybrid. The isozyme pattern obtained for L-iditol dehydrogenase (IDDH, E.C. 1.1.1.14), phosphoglucomutase (PGM, E.C. 5.4.2.2) and a fast migrating aspartate aminotransferase (AAT, E.C. 2.6.1.1) isozyme showed that this individual had both walleye and sauger isozymes. Isozyme analyses is a useful technique for distinguishing walleye x sauger hybrids from parent species. This is the first report of alleles of the AAT* locus being species specific for sauger and walleye, and the first confirmed report of naturally occurring walleye x sauger hybrids in Minnesota

Efficiency tests on gasoline engine

Citation: Stauffer, Arthur S., Matthews, Vernon, and Blair, Otis Neel. Efficiency tests on gasoline engine. Senior thesis, Kansas State Agricultural College, 1904.Morse Department of Special CollectionsIntroduction: This is a horizontal, ten horse power engine of the usual four cycle type, ignition taking place every fourth stroke and the speed being governed by cutting out charges of gasoline, (commonly called the “hit and miss" method) The following tests were made to determine the mechanical efficiency and the amount of gasoline required. The cylinder is cooled by city water direct from the hydrant. The temperatures of the cooling water were not taken as no attempt was made to determine the thermal efficiency of the engine. In the first two tests the load was applied by means of the ordinary prony brake, but as there was no provision for cooling the brake it, heated too badly for satisfactory results. In place of this was substituted a brake as shown in the frontispiece. This is a leather strap passing part way around the flywheel, the pull being recorded on a platform scale. By varying the arc of contract, the operator is enabled to maintain a steady load upon the engine