November 2, 2011
The 2011 Society for Neuroscience (SfN) Annual Meeting, Neuroscience 2011, is being held in Washington, D.C. from November 12th-16th. Neuroscience 2011 is the premier venue for neuroscientists from around the world to debut cutting-edge research on the brain and nervous system.
On Wednesday, November 16th, Elizabeth Eberle, Ph.D., Manager, Neuroscience and Oncology Operations at Covance Discovery and Translational Services, will be making a presentation, "UVB-Irradiation Induced Mechanical Allodynia and Thermal Hyperalgesia in the Rat: Correlation of Behavior and Pathology with Expression and miRNA Profiles for Pain Biomarker Discovery."Dr. Eberle's abstract is below:
Background: Ultraviolet-B (UVB) irradiation is known to cause reversible hypersensitivity to noxious thermal and mechanical stimuli. Localized UVB irradiation causes unilateral hyperalgesia/allodynia as well as bilateral stimulation of inflammatory mediators. In addition, miRNA levels are reported to be altered in other models of neuropathic and inflammatory pain. In the present study, behavioral responses were correlated with mRNA expression and miRNA profiles in a model of UVB-irradiation induced mechanical allodynia (MA) and Hargreaves’ model of thermal hyperalgesia (HTH) in order to identify potential biomarkers of pain. Methods: For validation of behavioral model endpoints, rats were given 200, 350 or 500 mJ UVB irradiation to one paw and the contralateral paw was untreated. MA and HTH were measured 2, 4, and 7 days post-irradiation. At multiple time points post-350 mJ UVB exposure, plantar skin and dorsal root ganglia were harvested bilaterally for miRNA and transcription profiling. Plasma was also collected from these animals for miRNA profiling. Additional validation of behavioral parameters was performed using ibuprofen treatment for HTH and Neurontin® for MA 2-days post-350 mJ UVB exposure. Expression profiling using NuGEN Ovation amplification was conducted using custom rat microarrays. miRNA profiling was performed with Exiqon whole rat genome qPCR microarrays. Results: UVB irradiation resulted in robust, predictable, drug responsive MA, HTH, and characteristic histopathology. Unilateral HTH was transient with a maximum response at 2 days post-UVB exposure. In contrast, unilateral MA persisted for the seven day period post UVB exposure. Ibuprofen (100 mg/kg) significantly increased paw withdrawal latency in HTH, while Neurontin® (10, 100 mg/kg) significantly increased paw withdrawal threshold in the MA model. Corresponding alterations in mRNA and miRNA profiles are being validated. Conclusions: UVB irradiation-induced MA and HTH are robust models of inflammatory pain. Correlation of behavioral responses and pathology with validated mRNA and miRNA profiles in these models may yield significant novel biomarkers of pain.
Additionally, four other posters from Covance scientists will be at SfN:
The selective mGlu2/3 receptor agonist LY379268 produces divergent basal and ketamine-evoked local cerebral glucose utilization in rats.
J. A. Meyer, J. Peters, J. Horn, J. Monn, D. McKinzie, K. Svensson, P. Territo, B. Gitter
NMDA receptor antagonists, such as ketamine (KA) and PCP, elicit schizophrenia-like behavior in animal models predictive of therapeutic efficacy in psychiatric disorders. In addition, normal volunteers exhibit a classical spectrum of schizophrenia symptoms following KA administration. Atypical antipsychotic agents and highly selective and potent group II metabotropic glutamate (mGlu) 2/3 receptor agonists, such as LY379268, are active in these predictive animal models and recently, the mGlu2/3 agonist, LY2140023, showed efficacy in schizophrenia patients. To understand how these compounds affect brain circuits thought to be involved in symptom clusters associated with schizophrenia, investigators are able to map neuroanatomical substrates using [14C]-2-deoxyglucose (2DG) autoradiography to measure drug effects on local cerebral glucose utilization (LCGU). Previous studies in rats showed global reductions in basal LCGU following treatment with clozapine (CZ) or the selective mGlu 2/3 agonist LY354740, but an alternative mGlu 2/3 agonist, LY379268 stimulated basal LCGU in several brain regions. However, relevance to both preclinical models of psychosis and clinical schizophrenia symptom clusters may be more appropriately assessed in a system that utilizes KA evocation. In the present study, the effects of 1, 3, and 10 mg/kg LY379268 and 1, 5, and 10 mg/kg of the atypical antipsychotic, CZ were compared on basal and KAevoked LCGU in the rat. LY379268, CZ, or vehicle (n=8/group) were administered i.p. 1 h and 2 h, respectively, prior to i.v. dosing with vehicle or KA (25 mg/kg) and 2DG tracer. Estimates of regional glucose metabolic rates in the target brain regions involved in psychosis and cognition were generated using the PK/PD model of Sokoloff et al. (1977). CZ treatment produced expected, albeit modest, dose-dependent reductions in KA-evoked LCGU in various cortical and thalamic regions. In contrast, LY379268 stimulated basal LCGU in multiple brain regions with peak effects (80-170%) observed in the 3 mg/kg dose group. However, LY379268 dose-dependently and robustly reversed KA-evoked LCGU in multiple brain regions down to pre-evoked levels in several areas, at doses comparable to the previously reported effects of the compound in preclinical models of psychosis. It’s presently unclear why LY379268 produced divergent effects on basal and KA-evoked LCGU. KA evocation (and, perhaps psychosis behavior in schizophrenia patients) may mask compound stimulated metabolism. Nevertheless, our model of KAevoked LCGU may provide a more disease-relevant understanding of mGlu receptor-mediated effects.
The muscarinic receptor agonist, xanomeline, reverses ketamine-evoked glucose metabolism in rats in specific brain regions at doses active in behavioral models of psychosis.
J. Horn, J. Peters, J. Meyer, D. Shaw, K. Knitowski, C. Felder, B. D. Gitter, D. McKinzie.
The muscarinic cholinergic system interacts with cortico-limbic dopamine receptors and has been implicated as a potential pharmacotherapy for the treatment of schizophrenia. The muscarinic M1/M4-preferring orthosteric receptor agonist xanomeline exhibits atypical-like antipsychotic actions in behavioral and neurochemical animal models (Stanhope et al, 2001; Perry et al, 2001). This predicted antipsychotic activity, based on preclinical findings, translated into a positive proof-of-concept clinical schizophrenia trial (Shekhar et al., 2008). Muscarinic M1 receptors interact cooperatively with NMDA receptors, yet few data are available demonstrating functional effects of xanomeline in NMDA antagonist-based models of psychosis. In the present study, we examined the dose-dependent effects of the muscarinic receptor agonist, xanomeline (3, 10, 30 mg/kg) in a rat model of ketamineevoked local cerebral glucose utilization (LCGU). Xanomeline or vehicle (n=8/group) were administered (via i.p. injection) 1 hr prior to i.v. dosing with ketamine (25 mg/kg) and [14C]-2-deoxy-glucose. Estimates of regional glucose metabolic rates in the target brain regions involved in psychosis and cognition were generated using the PK/PD model of Sokoloff et al. (1977). In multiple brain regions thought to be dysregulated in schizophrenia (e.g., prefrontal cortex, cingulate cortex, and nucleus accumbens), xanomeline attenuated ketamine-evoked LCGU by 20-30% at 10 and 30 mg/kg. Xanomeline was also tested in rodent dopamine (i.e., conditioned avoidance responding; CAR) and NMDA (i.e., phencyclidine-induced locomotor activity; PCP LMA) pharmacology models of psychosis. Notably, xanomeline reversed ketamine-evoked LCGU at doses comparable to those needed for activity in CAR and PCP LMA assays. These results indicate that xanomeline exerts antipsychotic-like actions upon both dopamine and glutamate neural pathways thought to be dysregulated in schizophrenia.
GABAA alpha-5 receptor occupancy of a GABAA alpha-5 agonist: Receptor occupancy studies using Ro 15-4513 as a tracer.
S. Rosenzweig-Lipson, P. Love, M. Teng Koh, M. Watson, J. Leander, M. Gallagher.
The present studies were conducted to validate the use of Ro 15-4513 as a tracer to measure GABAA alpha-5 receptor occupancy of compounds using LC-MS/MS and to characterize the receptor occupancy profile of a GABAA alpha-5 receptor agonist used in vivo to treat age-related memory impairment in rodents. Ro 15-4513 (0.3 - 20µg/kg, iv) was administered at multiple survival intervals to evaluate tracer distribution and dosing conditions to achieve the optimal binding potential. Consistent with GABAA alpha-5 receptor distribution, LC-MS/MS quantification of Ro 15-4513 demonstrated that Ro 15-4513 was differentially distributed in rat brain, with higher concentrations occurring in hippocampus relative to cerebellum. Administration of 1µg/kg, iv of Ro 15-4513 at the 20-minute survival interval produced the largest total/null ratio and was chosen for further experiments. Two GABAA alpha-5 inverse agonist modulators (L-655,708 and MRK 016) were administered prior to tracer administration to determine if Ro 15-4513 tracer binding was indicative of GABAA alpha-5 receptor occupancy. Both compounds (0.01 - 10 mg/kg, iv, 60’ pre) dose dependently inhibited the Ro 15-4513 tracer signal in hippocampus, indicative of GABAA alpha-5 receptor occupancy. The selective GABAA alpha-5 compound, L-655,708 did not inhibit the tracer signal in cerebellum, whereas the nonselective compound, MRK 016 also inhibited the tracer signal in cerebellum. A novel GABAA alpha-5 agonist modulator (5-fold selective vs GABAA alpha-3 and 12-fold selective vs GABAA alpha-1) (referred to as “Compound 6” in van Niel et al., 2005) has shown efficacy in cognition models in aged rats (Koh and Gallagher, 2010).“Compound 6” (0.01 - 10 mg/kg, iv) dose dependently inhibited the Ro 15-4513 tracer signal in hippocampus, but not cerebellum, indicative of GABAA alpha-5 receptor occupancy. “Compound 6” showed excellent brain penetration with B/P ratios of 3 and 1.3 at 1 and 10 mg/kg, iv, respectively. Results of the present studies demonstrate that Ro 15-4513 is an appropriate tracer for evaluation of GABAA alpha-5 receptor occupancy and that “Compound 6” is present in brain and occupies GABAAalpha-5 receptors.
Semi-automated osteoarthritis model for drug candidate screening.
R. L. Hunter, E. A. Misener, H. E. Shannon, M. J. Kallman.
Osteoarthritis (OA) is a degenerative disease of joint cartilage and its underlying bone. An aging population and no cure for OA have lead to exorbitant socioeconomic costs associated with the disease. Present treatments focus on improving function and providing pain relief but these therapies come with detrimental side-effects. New drugs need to be developed to successfully treat this disease. Various models exist to study mechanismsrelated to OA, and monosodium iodoacetate (MIA) injection into a rat’s knee represents one clinically relevant disease model. The histopathology from the MIA model shows joint degeneration that is similar to that seen in the human condition and weight bearing can be used as an index of pain. Therefore, MIA injection and weight bearing can be used as a clinically relevant behavioral assay for screening potential OA drug candidates. However, reproducibility issues appear in the literature for the MIA model. Here we developed a stable and reproducible MIA model that can be used for screening drug candidates with the potential to treat OA-related pain. MIA (2mg) injection into the knee generates a reproducible unilateral OA model with stability across time for measuring the difference in weight bearing. Both morphine and neurontin attenuate the MIA-induced difference in weight bearing when dosed and tested within the pharmacologically active window. In summary our 2 mg MIA-induced OA model provides stable and reproducible differences in weight bearing that can be used as a tool for screening potential OA painrelated drug candidates.