2-3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline and Inflammation

Oxytocin (OT) is a neuropeptide elaborated by the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei. Magnocellular OT neurons of these nuclei innervate numerous forebrain regions and release OT into the blood from the posterior pituitary. The PVN also harbors parvocellular OT cells that project to the brainstem and spinal cord, but their function has not been directly assessed. Here, we identified a subset of approximately 30 parvocellular OT neurons, with collateral projections onto magnocellular OT neurons and neurons of deep layers of the spinal cord. Evoked OT release from these OT neurons suppresses nociception and promotes analgesia in an animal model of inflammatory pain. Our findings identify a new population of OT neurons that modulates nociception in a two tier process: (1) directly by release of OT from axons onto sensory spinal cord neurons and inhibiting their activity and (2) indirectly by stimulating OT release from SON neurons into the periphery.

Topics: Action Potentials; Animals; Cholecystokinin; Disease Models, Animal; Excitatory Amino Acid Antagonists; Gene Expression Regulation; Inflammation; Neural Pathways; Neuralgia; Neurons; Oxytocin; Paraventricular Hypothalamic Nucleus; Quinoxalines; Rats; Rats, Wistar; Receptors, Oxytocin; Spinal Cord; Supraoptic Nucleus; Transduction, Genetic; Vasopressins; Vesicular Glutamate Transport Protein 2

Synovial fluid glutamate concentrations increase in arthritis. Activation of kainate (KA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptors (GluRs) increase interleukin-6 (IL-6) release and cause arthritic pain, respectively. We hypothesised that AMPA and KA GluRs are expressed in human arthritis, and that intra-articular NBQX (AMPA/KA GluR antagonist) prevents pain and pathology in antigen-induced arthritis (AIA).. GluR immunohistochemistry was related to synovial inflammation and degradation in osteoarthritis (OA) and rheumatoid arthritis (RA). A single intra-articular NBQX injection was given at induction, and knee swelling and gait of AIA and AIA+NBQX rats compared over 21 days, before imaging, RT-qPCR, histology and immunohistochemistry of joints. Effects of NBQX on human primary osteoblast (HOB) activity were determined.. AMPAR2 and KA1 immunolocalised to remodelling bone, cartilage and synovial cells in human OA and RA, and rat AIA. All arthritic tissues showed degradation and synovial inflammation. NBQX reduced GluR abundance, knee swelling (p<0.001, days 1-21), gait abnormalities (days 1-2), end-stage joint destruction (p<0.001), synovial inflammation (p<0.001), and messenger RNA expression of meniscal IL-6 (p<0.05) and whole joint cathepsin K (p<0.01). X-ray and MRI revealed fewer cartilage and bone erosions, and less inflammation after NBQX treatment. NBQX reduced HOB number and prevented mineralisation.. AMPA/KA GluRs are expressed in human OA and RA, and in AIA, where a single intra-articular injection of NBQX reduced swelling by 33%, and inflammation and degeneration scores by 34% and 27%, respectively, exceeding the efficacy of approved drugs in the same model. AMPA/KA GluR antagonists represent a potential treatment for arthritis.

Topics: Animals; Arthritis, Experimental; Arthritis, Rheumatoid; Behavior, Animal; Cartilage, Articular; Excitatory Amino Acid Antagonists; Humans; Immunohistochemistry; Inflammation; Interleukin-6; Knee Joint; Male; Menisci, Tibial; Osteoarthritis; Osteoblasts; Pain; Quinoxalines; Radiography; Rats; Receptors, AMPA; Receptors, Kainic Acid; Synovial Membrane

Inflammation influences several steps of adult neurogenesis, but whether it regulates the functional integration of the new neurons is unknown. Here, we explored, using confocal microscopy and whole-cell patch-clamp recordings, whether a chronic inflammatory environment affects the morphological and electrophysiological properties of new dentate gyrus granule cells, labeled with a retroviral vector encoding green fluorescent protein. Rats were exposed to intrahippocampal injection of lipopolysaccharide, which gave rise to long-lasting microglia activation. Inflammation caused no changes in intrinsic membrane properties, location, dendritic arborization, or spine density and morphology of the new cells. Excitatory synaptic drive increased to the same extent in new and mature cells in the inflammatory environment, suggesting increased network activity in hippocampal neural circuitries of lipopolysaccharide-treated animals. In contrast, inhibitory synaptic drive was more enhanced by inflammation in the new cells. Also, larger clusters of the postsynaptic GABA(A) receptor scaffolding protein gephyrin were found on dendrites of new cells born in the inflammatory environment. We demonstrate for the first time that inflammation influences the functional integration of adult-born hippocampal neurons. Our data indicate a high degree of synaptic plasticity of the new neurons in the inflammatory environment, which enables them to respond to the increase in excitatory input with a compensatory upregulation of activity and efficacy at their afferent inhibitory synapses.

Topics: Analysis of Variance; Animals; Calcium-Binding Proteins; Dendritic Spines; Dose-Response Relationship, Radiation; Ectodysplasins; Electric Stimulation; Electroencephalography; Excitatory Amino Acid Antagonists; Excitatory Postsynaptic Potentials; Green Fluorescent Proteins; Hippocampus; In Vitro Techniques; Inflammation; Inhibitory Postsynaptic Potentials; Lipopolysaccharides; Lysine; Male; Microfilament Proteins; Microscopy, Confocal; Neurogenesis; Neurons; Patch-Clamp Techniques; Quinoxalines; Rats; Rats, Sprague-Dawley; Seizures; Tetrodotoxin; Time Factors

To examine the possible role of inflammatory cytokines in mediating neonatal brain injury, we investigated effects of intracerebral injection of IL-1beta (IL-1beta) or tumor necrosis factor-alpha (TNFalpha) on brain injury in the neonatal rat. A stereotaxic intracerebral injection of IL-1beta or TNFalpha (10 ng per pup) was performed in postnatal day 5 (P5) SD rats. Although no necrosis of neurons was found, increased astrogliosis, as indicated by GFAP positive staining was observed 24 and 72 h following the injection of IL-1beta or TNFalpha. IL-1beta induced apoptotic cell death in the rat brain 24 h after the injection, as indicated by increases in positive TUNEL staining and caspase-3 activity, and apoptotic cell death was partially blocked by systemic administration of NBQX, an antagonist of the AMPA glutamate receptor. IL-1beta also significantly reduced the number of developing oligodendrocytes (OLs) 24 h after the injection and this impairment was not prevented by NBQX. On the contrary, TNFalpha induced a much smaller increase in the number of TUNEL positive cells and did not reduce the number of developing OLs. By P8, myelin basic protein (MBP) was clearly detected in the control rat brain, while MBP positive staining was very weak, if any, in the IL-1beta treated rat brain. MBP expression in the TNFalpha treated rat brain was less affected. The overall results indicate that IL-1beta may directly cause injuries to developing OLs and impair myelination in the neonatal rat brain and TNFalpha may have different roles in mediating brain injury.

Topics: Animals; Animals, Newborn; Apoptosis; Brain Injuries; Caspase 3; Caspases; Cerebral Cortex; Excitatory Amino Acid Antagonists; Humans; In Situ Nick-End Labeling; Infant; Inflammation; Interleukin-1; Myelin Basic Protein; Oligodendroglia; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, AMPA; Tumor Necrosis Factor-alpha

The relative contribution of the NMDA/glycine allosteric site and non-NMDA (AMPA) types of glutamate receptor to the acute and tonic phases of the behavioural nociceptive response to formalin has been studied in the rat. The AMPA receptor selective antagonist NBQX preferentially inhibited the acute phase indicating that AMPA receptors may be involved in mediating fast acute nociceptive transmission in the dorsal horn. In contrast, the strychnine-insensitive glycine site partial agonist (+)-HA-966 and the NMDA competitive antagonist CGS 19755 preferentially attenuated the tonic nociceptive phase. However, none of these compounds exhibited anti-inflammatory properties. Thus, both NMDA and non-NMDA antagonists can selectively block changes in neuronal excitability while tissue injury in the receptive field continues to evolve.

Topics: Analgesics; Animals; Formaldehyde; Inflammation; Male; N-Methylaspartate; Nociceptors; Pain Measurement; Pipecolic Acids; Pyrrolidinones; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; Receptors, Glutamate; Receptors, Glycine; Receptors, N-Methyl-D-Aspartate