Neuroscience
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A novel calmodulin (CaM) antagonist DY-9760e, (3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1-(4-imidazolylmethyl)-1H-indazole dihydrochloride 3.5 hydrate), with an apparent neuroprotective effect in vivo, potently inhibits CaM-dependent nitric oxide synthase in situ. In the present study, we determined whether DY-9760e inhibits nitric oxide (NO) production and protein nitration by peroxynitrite (ONOO(-)) formation in the hippocampal CA1 region of gerbils after transient forebrain ischemia. In freely moving gerbils, NO production after 10-minute forebrain ischemia was monitored consecutively with in vivo brain microdialysis. ⋯ Western blot and immunohistochemical analyses using an anti-nitrotyrosine antibody as a marker of ONOO(-) formation indicated a marked increase in nitrotyrosine immunoreactivity in the pyramidal neurons of the CA1 region 2 h after reperfusion, and DY-9760e significantly inhibited increased nitrotyrosine immunoreactivity. Coincident with the inhibition of the NO production and protein tyrosine nitration, pretreatment with DY-9760e rescued the delayed neuronal death in the hippocampal CA1 region. These results suggest that the inhibitory effects of DY-9760e on the NO-ONOO(-) pathway partly account for its neuroprotective effects in cerebral ischemia.
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Comparative Study
Role of postsynaptic density protein-95 in the maintenance of peripheral nerve injury-induced neuropathic pain in rats.
Our previous work has demonstrated that postsynaptic density protein-95, a molecular scaffolding protein that binds and clusters N-methyl-D-aspartate receptors at neuronal synapses, plays an important role in the development of peripheral nerve injury-induced neuropathic pain. The current study further investigated the possible involvement of postsynaptic density protein-95 in the maintenance of neuropathic pain. Mechanical and thermal hyperalgesia were induced within 3 days and maintained for 15 days or longer after unilateral injury to the fifth lumbar spinal nerve. ⋯ In addition, postsynaptic density protein-95 antisense oligodeoxynucleotide did not change locomotor activity of experimental animals. Our results indicate that the deficiency of postsynaptic density protein-95 protein in the spinal cord significantly attenuates nerve injury-induced mechanical and thermal hyperalgesia during both the development and maintenance of chronic neuropathic pain. These results suggest that postsynaptic density protein-95 might be involved in the central mechanisms of chronic neuropathic pain and provide a novel target for development of new pain therapies.
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Comparative Study
Effects of extracellular atp on axonal transport in cultured mouse dorsal root ganglion neurons.
In primary sensory neurons, extracellular ATP plays important roles in nociception and afferent neurotransmission. Here we investigated the effects of ATP on axonal transport in cultured adult mouse dorsal root ganglion neurons using video-enhanced microscopy. Continuous application (26 min) of ATP (100 microM) significantly increased axonal transport of membrane-bound organelles in anterograde and retrograde directions. ⋯ Our findings indicate that extracellular ATP is able to increase axonal transport in primary sensory neurons. The equal potency of ATP and UTP with no detectable response to ADP, alpha,beta-methylene ATP, or 2-methylthio ATP suggests the possible involvement of P2Y(2) receptors. Extracellular ATP may play an important role in the modulation of axonal transport in sensory neurons.
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Cisplatin, a commonly used antineoplastic agent, destroys the sensory hair cells in the cochlear and vestibular system leading to irreversible hearing loss and balance problems. Cisplatin-induced hair cell damage presumably occurs by apoptosis. Recent studies suggest that p53 may play an important role initiating cisplatin-induced apoptosis in some cell types. ⋯ Addition of PFT (20-100 microM) to cisplatin-treated cochlear and utricular cultures resulted in a dose-dependent increase in hair cell survival; suppressed the expression of p53 in Western blots and eliminated caspase-1 and caspase-3 labeling in cultures. These results suggest that the tumor suppressor protein, p53, plays a critical role in initiating apoptosis in cochlear and vestibular hair cells. Temporary suppression of p53 with PFT provides significant protection against cisplatin-induced hair cell loss and offers the potential for reducing the ototoxic, vestibulotoxic and neurotoxic side effects of cisplatin.
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Comparative Study
A peripheral cannabinoid mechanism suppresses spinal fos protein expression and pain behavior in a rat model of inflammation.
The present studies were conducted to test the hypothesis that systemically inactive doses of cannabinoids suppress inflammation-evoked neuronal activity in vivo via a peripheral mechanism. We examined peripheral cannabinoid modulation of spinal Fos protein expression, a marker of neuronal activity, in a rat model of inflammation. Rats received unilateral intraplantar injections of carrageenan (3%). ⋯ The suppressive effects of WIN55,212-2 (30 microg intraplantarly) on carrageenan-evoked Fos protein expression and pain behavior were blocked by local administration of either the CB(2) antagonist SR144528 (30 microg intraplantarly) or the CB(1) antagonist SR141716A (100 microg intraplantarly). WIN55,212-3, the enantiomer of the active compound, also failed to suppress carrageenan-evoked Fos protein expression. These data provide direct evidence that a peripheral cannabinoid mechanism suppresses the development of inflammation-evoked neuronal activity at the level of the spinal dorsal horn and implicate a role for CB(2) and CB(1) in peripheral cannabinoid modulation of inflammatory nociception.