Neuroscience
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The Edinger-Westphal nucleus is the primary source of urocortin in rodent brain. Mapping of inducible transcription factors has shown that the Edinger-Westphal nucleus is preferentially sensitive to ethanol self-administration. In the present study we have immunohistochemically compared expression of urocortin and c-Fos in naive and ethanol-treated C57BL/6J and DBA/2J mouse inbred strains. ⋯ Behavioral analysis of the B6D2 F2 intercross, a heterogeneous mouse strain, showed that the number of urocortin cells is positively correlated with basal temperatures and ethanol-induced hypothermia. Involvement of the Edinger-Westphal in alcohol-induced hypothermia is further confirmed by analysis of urocortin cells in the HOT/COLD selected lines. These results provide evidence that C57BL/6J and DBA/2J mice have structural differences in the Edinger-Westphal that can result in activation of different populations of neurons upon alcohol intoxication contributing to differential thermoregulation between these inbred strains.
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Evidence for the participation of Rel/NF-kappaB transcription factors in long-term memory has recently been reported in the context-signal learning paradigm of the crab Chasmagnathus, in which a high correlation between long-term memory formation and NF-kappaB activation was observed. Two components of the NF-kappaB pathway in the crab brain have now been identified by cross-immunoreactivity using mammalian antibodies for IkappaB-alpha and IkappaB kinase alpha. Furthermore, IkappaB kinase-like phosphotransferase activity, which was inhibited by the IkappaB kinase inhibitor sulfasalazine, was detected in brain extracts. ⋯ In vivo sulfasalazine inhibition of basal NF-kappaB activity was found between 30 and 45 min after injection, as assessed by electrophoretic mobility shift assay. On the other hand, in vivo sulfasalazine administration 6 h after training inhibited the second phase of training-induced NF-kappaB activation, providing evidence that the sulfasalazine effect on memory is due to a direct effect of the drug on the NF-kappaB pathway. These results provide the first evidence that IkappaB kinase and NF-kappaB activation are necessary for memory formation.
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beta-Endorphin is a non-selective opioid peptide which binds mu-, delta- and putative epsilon (beta-endorphin-sensitive non-mu-, non-delta- and non-kappa(1)-)-opioid receptors. We have previously reported that beta-endorphin-produced G-protein activation is mediated by the stimulation of both mu- and putative epsilon-opioid receptors. The present study was designed to further characterize this putative epsilon-opioid receptor-mediated G-protein activation in the pons/medulla membrane obtained from mice lacking mu-opioid receptor, using a guanosine-5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPgammaS)-binding assay. beta-Endorphin and the mu-opioid receptor agonist [D-Ala(2),N-MePhe(4),Gly-ol(5)]enkephalin (DAMGO) increased the [(35)S]GTPgammaS binding in a concentration-dependent manner (0.001-10 microM), and at 10 microM beta-endorphin and DAMGO produced approximately 250 and 120% increases of [(35)S]GTPgammaS binding in the pons/medulla membrane obtained from wild-type mice, respectively. ⋯ The residual increase in [(35)S]GTPgammaS binding by 10 microM beta-endorphin in mu-opioid receptor knockout mice was partially but significantly attenuated by the putative epsilon-opioid receptor partial agonist beta-endorphin (1-27), but not by the delta-opioid receptor antagonist naltrindole or the kappa(1)-receptor antagonist norbinaltorphimine. Furthermore, buprenorphine significantly attenuated the residual increase in [(35)S]GTPgammaS binding by 10 microM beta-endorphin in mu-opioid receptor knockout mice. The present results indicate that beta-endorphin activates G-protein by stimulation of putative epsilon-opioid receptors in the condition lacking the mu-opioid receptor, and buprenorphine acts as an antagonist for putative epsilon-opioid receptors in this condition.
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Annexins and S100 proteins constitute two multigenic families of Ca2+-modulated proteins that have been implicated in the regulation of both intracellular and extracellular activities. Some annexins can interact with certain S100 protein dimers thereby forming heterotetramers in which an S100 dimer crosslinks two copies of the partner annexin. It is suggested that S100 protein binding to an annexin might serve the function of regulating annexin function and annexin binding to an S100 protein might regulate S100 function. ⋯ Immunoprecipitation studies indicated that ANXA6/S100A1 and ANXA6/S100B complexes formed in vivo. Whereas, ANXA5 was not recovered in S100A1 or S100B immunoprecipitates. From our data we suggest that: (i) ANXA5 and ANXA6, and S100A1 and S100B can be used as markers of skeletal muscle development; (ii) ANXA6 and S100A1 and S100B appear strategically located close to or on skeletal muscle membrane organelles that are critically involved in the regulation of Ca2+ fluxes, thus supporting previous in vitro observations implicating S100A1 and ANXA6 in the stimulation of Ca2+-induced Ca2+ release; and (iii) ANXA6/S100A1 and ANXA6/S100B complexes can form in vivo thereby regulating each other activities and/or acting in concert to regulate membrane-associated activities.
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Comparative Study
The influence of chemical sympathectomy on pain responsivity and alpha 2-adrenergic antinociception in neuropathic animals.
We studied the effect of chemical sympathectomy by 6-hydroxydopamine (6-OHDA) on pain behavior and alpha(2)-adrenergic antinociception in rats with a spinal nerve ligation-induced neuropathy. For assessment of alpha(2)-adrenergic antinociception, the rats were treated systemically with two alpha(2)-adrenoceptor agonists, one of which only poorly (MPV-2426) and the other very well (dexmedetomidine) penetrates the blood-brain barrier. Moreover, the effect of MPV-2426 on spontaneous activity of dorsal root nerve fibers proximal to the nerve injury was determined. ⋯ MPV-2426-induced modulation of spontaneous activity was not a general property of dorsal root fibers proximal to the injury. The results indicate that a chemical destruction of sympathetic postganglionic nerve fibers innervating the skin does not markedly influence cutaneous pain sensitivity nor is it critical for the alpha(2)-adrenoceptor agonist-induced attenuation of pain behavior in neuropathic or non-neuropathic animals. Chemical sympathectomy, independent of neuropathy, enhanced the pain attenuating effect by MPV-2426, probably due to a peripheral action, whereas in non-sympathectomized control and neuropathic animals peripheral mechanisms have only a minor, if any, role in the alpha(2)-adrenoceptor agonist-induced antinociception.