Inhibition of AAK1 Kinase as a Novel Therapeutic Approach to Treat Neuropathic Pain.

To identify novel targets for neuropathic pain, 3097 mouse knockout lines were tested in acute and persistent pain behavior assays. One of the lines from this screen, which contained a null allele of the adapter protein-2 associated kinase 1 (AAK1) gene, had a normal response in acute pain assays (hot plate, phase I formalin), but a markedly reduced response to persistent pain in phase II formalin. AAK1 knockout mice also failed to develop tactile allodynia following the Chung procedure of spinal nerve ligation (SNL).

Diacylglycerol Lipase α Knockout Mice Demonstrate Metabolic and Behavioral Phenotypes Similar to Those of Cannabinoid Receptor 1 Knockout Mice.

After creating >4,650 knockouts (KOs) of independent mouse genes, we screened them by high-throughput phenotyping and found that cannabinoid receptor 1 (Cnr1) KO mice had the same lean phenotype published by others. We asked if our KOs of DAG lipase α or β (Dagla or Daglb), which catalyze biosynthesis of the endocannabinoid (EC) 2-arachidonoylglycerol (2-AG), or Napepld, which catalyzes biosynthesis of the EC anandamide, shared the lean phenotype of Cnr1 KO mice. We found that Dagla KO mice, but not Daglb or Napepld KO mice, were among the leanest of 3651 chow-fed KO lines screened.

Novel inhibitors of the high-affinity L-proline transporter as potential therapeutic agents for the treatment of cognitive disorders.

The incidence of cognitive disorders such as Alzheimer's disease continues to increase unabated. While cures for such diseases have eluded investigators, progress is being made on alleviating certain symptoms of these diseases. Mouse knockouts of the proline transporter (PROT), a high affinity Na(+)/Cl(-)-dependent transporter, indicated its potential as a novel therapeutic target for cognition improvement.

Ligation of mouse L4 and L5 spinal nerves produces robust allodynia without major motor function deficit.

Spinal nerve L5/L6 ligation (SNL) in rats has become the standard for mechanistic studies of peripheral neuropathy and screening for novel analgesics. Conventional SNL in our hybrid mice resulted in a wide range of allodynia. Anatomical evaluation indicated that a variable number of lumbar vertebrae existed, resulting in L4/L5 or L5/L6 being ligated.

Characterization of PTPRG in knockdown and phosphatase-inactive mutant mice and substrate trapping analysis of PTPRG in mammalian cells.

Receptor tyrosine phosphatase gamma (PTPRG, or RPTPγ) is a mammalian receptor-like tyrosine phosphatase which is highly expressed in the nervous system as well as other tissues. Its function and biochemical characteristics remain largely unknown. We created a knockdown (KD) line of this gene in mouse by retroviral insertion that led to 98-99% reduction of RPTPγ gene expression.

A high-throughput screen for receptor protein tyrosine phosphatase-gamma selective inhibitors.

Protein tyrosine phosphatase-γ (PTP-γ) is a receptor-like PTP whose biological function is poorly understood. A recent mouse PTP-γ genetic deletion model associated the loss of PTP-γ gene expression with a potential antidepressant phenotype. This led the authors to screen a subset of the Bristol-Myers Squibb (BMS) compound collection to identify selective small-molecule inhibitors of receptor-like PTP-γ (RPTP-γ) for use in evaluating enzyme function in vivo.

Viable mouse gene ablations that robustly alter brain Aβ levels are rare.

Background: Accumulation of amyloid-β (Aβ) peptide in the brain is thought to play a key pathological role in Alzheimer's disease. Many pharmacological targets have therefore been proposed based upon the biochemistry of Aβ, but not all are equally tractable for drug discovery.

Results: To search for novel targets that affect brain Aβ without causing toxicity, we screened mouse brain samples from 1930 novel gene knock-out (KO) strains, representing 1926 genes, using Aβ ELISA assays.

Transmembrane and ubiquitin-like domain containing 1 (Tmub1) regulates locomotor activity and wakefulness in mice and interacts with CAMLG.

Tmub1 (C7orf21/HOPS) encodes a protein containing a ubiquitin-like domain. Tmub1 is highly expressed in the nervous system. To study its physiological function, we generated mice with Tmub1 deleted by homologous recombination.

Male and female Fmr1 knockout mice on C57 albino background exhibit spatial learning and memory impairments.

Impaired spatial learning is a prominent deficit in fragile X syndrome (FXS). Previous studies using the Fmr1 knockout (KO) mouse model of FXS have not consistently reported a deficit in spatial learning. Fmr1 KO mice bred onto an albino C57BL/6J-Tyr(c-Brd) background showed significant deficits in several primary measures of performance during place navigation and probe trials in the Morris water maze.

Loss of the putative catalytic domain of HDAC4 leads to reduced thermal nociception and seizures while allowing normal bone development.

Histone deacetylase 4 (HDAC4) has been associated with muscle & bone development [1]-[6]. N-terminal MEF2 and RUNX2 binding domains of HDAC4 have been shown to mediate these effects in vitro. A complete gene knockout has been reported to result in premature ossification and associated defects resulting in postnatal lethality [6].

Discovery and characterization of potent small molecule inhibitors of the high affinity proline transporter.

The mammalian proline transporter (PROT) is a high affinity Na(+)/Cl(-)-dependent transporter expressed in specific regions of the brain. It is homologous to other neurotransmitter transporters such as glycine, norepinephrine, serotonin, and dopamine transporters. PROT is enriched in glutamatergic synaptic terminals and may play an important role in the regulation of excitatory neurotransmission.

Differential sensitivity to SSRI and tricyclic antidepressants in juvenile and adult mice of three strains.

Clinical studies have shown differential efficacy of several antidepressants in children and adolescents compared to adults, yet few animal studies have sought to characterize this phenomenon. We compared effects of fluoxetine and imipramine in two common behavioral assays that hold high predictive validity for antidepressant activity, tail suspension and forced swim test, using juvenile (5 weeks) and adult (12 weeks) mice from 3 strains. C57BL/6J-Tyr(c-Brd) (C57), hybrid C57BL/6J-Tyr(c-Brd)x129S5/SvEvBrd (F2), and Balb/cAnNTac (Balb/C) mice were tested in forced swim test and tail suspension after i.

Genetic disruption of both tryptophan hydroxylase genes dramatically reduces serotonin and affects behavior in models sensitive to antidepressants.

The neurotransmitter serotonin (5-HT) plays an important role in both the peripheral and central nervous systems. The biosynthesis of serotonin is regulated by two rate-limiting enzymes, tryptophan hydroxylase-1 and -2 (TPH1 and TPH2). We used a gene-targeting approach to generate mice with selective and complete elimination of the two known TPH isoforms.

Learning and memory impairment in Eph receptor A6 knockout mice.

Genetic inhibition of the ephrin receptor (EphA6) in mice produced behavioral deficits specifically in tests of learning and memory. Using a fear conditioning training paradigm, mice deficient in EphA6 did not acquire the task as strongly as did wild type (WT) mice. When tested in the same context 24h later, knockout (KO) mice did not freeze as much as WT mice indicating reduced memory of the consequences of the training context.

Netrin-G2 and netrin-G2 ligand are both required for normal auditory responsiveness.

Mice in which netrin-G2 has been genetically inhibited do not startle to an acoustic stimulus, but otherwise perform normally through a behavioral test battery. Light microscopic examination of the inner ear showed no obvious structural abnormalities. Brainstem responses to acoustic stimuli (auditory brainstem responses, ABR) were also present, confirming the lack of any overarching defects in the inner ear or auditory nerve.

Use of a platform in an automated open-field to enhance assessment of anxiety-like behaviors in mice.

The present report describes a setup for simultaneously measuring anxiety-like behaviors and locomotor activity in mice. Animals are placed in a brightly lit, standard automated open-field (OF) in which a rectangular ceramic platform 8 cm high covers one quadrant of the floor. Mice preferred to stay under the platform, avoiding the area with bright illumination.

Insertion mutation at the C-terminus of the serotonin transporter disrupts brain serotonin function and emotion-related behaviors in mice.

The 5-hydroxytryptamine transporter (5-HTT) regulates 5-hydroxytryptamine (5-HT) neurotransmission by removing 5-HT from the synaptic cleft. Emerging evidence from clinical and genetic studies implicates the 5-HTT in various neuropsychiatric conditions, including anxiety and depression. Here we report that a 5-HTT null mutant mouse line was generated by gene trapping that disrupted the sequence encoding the C-terminus of 5-HTT.

Role of peripheral N-methyl-D-aspartate (NMDA) receptors in visceral nociception in rats.

Background & Aims: N-methyl-D-aspartate (NMDA) receptors are ligand-gated ion channels that have an important role in long-term potentiation and memory processing in the central nervous system. The aims in this study were to determine whether NMDA receptors are expressed in the peripheral nervous system and identify their role in mediating behavioral pain responses to colonic distention in the normal gut.

Methods And Results: Immunohistochemical localization of the NR1 subunit showed that NMDA receptors are expressed on the cell bodies and peripheral terminals of primary afferent nerves innervating the colon.

Structural modifications to an N-methyl-D-aspartate receptor antagonist result in large differences in trapping block.

Differences in the degree of trapping of initial block by N-methyl-D-aspartate (NMDA) receptor antagonists may affect their safety and, hence, suitability for clinical trials. In this comparative study, 23 compounds structurally related to the low-affinity, use-dependent NMDA receptor antagonist (S)-alpha-phenyl-2-pyridineethanamine dihydrochloride (AR-R15896AR) were examined to determine the degree of trapping block they exhibit. Compounds were tested at concentrations that produced a comparable initial 80% block of NMDA-mediated whole-cell current in rat cortical cultures.

The 5-HT3 antagonist tropisetron (ICS 205-930) is a potent and selective alpha7 nicotinic receptor partial agonist.

The 5-HT3 receptor antagonist tropisetron (ICS 205-930) was found to be a potent and selective partial agonist at alpha7 nicotinic receptors. Two other 5-HT3 receptor antagonists, ondansetron and LY-278,584, were found to lack high affinity at the alpha7 nicotinic receptor. Quinuclidine analogues (1 and 2) of tropisetron were also found to be potent and selective partial agonists at alpha7 nicotinic receptors.

Differences in degree of trapping between AR-R15896 and other uncompetitive NMDA receptor antagonists.

NMDA antagonists like AR-R15896 have been selected on the basis of their good therapeutic indices. As Dr. Rogawski has pointed out, there may be a number of molecular factors which can improve the therapeutic index of NMDA antagonists.

Distinct ATP-activated currents in different types of neurons dissociated from rat dorsal root ganglion.

Rat dorsal root ganglion neurons can be classified into at least three distinct groups based on cell size, afferent fiber diameter, electrophysiological properties, sensitivity to vanilloid agonists such as capsaicin, and function. In the present study, ATP-activated current in these neurons was characterized using whole-cell patch-clamp recording. Small diameter (<30 microm) cells had high capsaicin sensitivity, high affinity for ATP, and rapidly desensitizing ATP-activated current.

Differences in degree of trapping of low-affinity uncompetitive N-methyl-D-aspartic acid receptor antagonists with similar kinetics of block.

This study characterizes the trapping of block of N-methyl-D-aspartic acid (NMDA)-induced currents by three structurally distinct, use-dependent NMDA receptor antagonists with similar rapid on-off rates. The antagonism of whole-cell currents in cultured rat cortical neurons by AR-R15896AR, ketamine, and memantine was examined. All three compounds produced a steady-state block after a 30-s coapplication, which was fully relieved after 50 s of NMDA exposure.

Nicotinic agonists competitively antagonize serotonin at mouse 5-HT3 receptors expressed in Xenopus oocytes.

The 5-HT3 receptor (5-HT3R) is part of a superfamily of ligand-gated ion channels which includes nicotinic acetylcholine receptors (nAChR). cRNA derived from the long isoform cloned mouse 5-HT3R was used to drive expression of 5-HT3Rs in Xenopus oocytes. 5-HT-induced currents were monitored using two-electrode voltage-clamp.