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Extracellular Application (extracellular + application)
Selected AbstractsExtracellular cAMP inhibits P2X3 receptors in rat sensory neurones through G protein-mediated mechanismACTA PHYSIOLOGICA, Issue 2 2010M. V. Mamenko Abstract Aim:, To identify the mechanisms of P2X3 receptor inhibition by extracellular cyclic adenosine monophosphate (cAMP) in rat dorsal root ganglion (DRG) neurones. Methods:, Whole-cell currents were measured in cultured DRG neurones using the combination of voltage and concentration clamp. Results:, We have found that extracellular cAMP inhibits P2X3 -mediated currents in a concentration- and use-dependent manner. The P2X3 currents, activated by ATP applied every 4 min, were inhibited by 55% in the presence of 10 ,m cAMP and by 81% in the presence of 30 ,m cAMP. At 8 min interval between ATP applications the same concentration of cAMP did not alter the currents. Addition of 0.5 mm of guanosine 5,- O -(2-thiodiphosphate) to intracellular solution blocked the inhibitory action of cAMP. The inhibitory effects of cAMP were not mimicked by extracellular application of 30 ,m adenosine. Conclusions:, In this paper, we demonstrate, for the first time, that extracellular application of cAMP to rat sensory neurones inhibits P2X3 receptors via a G protein-coupled mechanism in a use-dependent manner, thus indicating the neuronal expression of specific plasmalemmal cAMP receptor. [source] Stabilizing effects of extracellular ATP on synaptic efficacy and plasticity in hippocampal pyramidal neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2005Eduardo D. Martín Abstract The role of adenosine triphosphate (ATP) as a neurotransmitter and extracellular diffusible messenger has recently received considerable attention because of its possible participation in the regulation of synaptic plasticity. However, the possible contribution of extracellular ATP in maintaining and regulating synaptic efficacy during intracellular ATP depletion is understudied. We tested the effects of extracellular ATP on excitatory postsynaptic currents (EPSCs) evoked in CA1 pyramidal neurons by Schaffer collateral stimulation. In the absence of intracellular ATP, EPSC rundown was neutralized when a low concentration of ATP (1 µm) was added to the extracellular solution. Adenosine and ATP analogues did not prevent the EPSC rundown. The P2 antagonists piridoxal-5,-phosphate-azophenyl 2,,4,-disulphonate (PPADS) and reactive blue-2, and the P1 adenosine receptor antagonist 8-cyclopentyltheophylline (CPT) had no detectable effects in cells depleted of ATP. However, the protective action of extracellular ATP on synaptic efficacy was blocked by extracellular application of the protein kinase inhibitors K252b and staurosporine. In contrast, K252b and staurosporine per se did not interfere with synaptic transmission in ATP loaded cells. Without intracellular ATP, bath-applied caffeine induced a transient (< 35 min) EPSC potentiation that was transformed into a persistent long-term potentiation (> 80 min) when 1 µm ATP was added extracellularly. An increased probability of transmitter release paralleled the long-term potentiation induced by caffeine, suggesting that it originated presynaptically. Therefore, we conclude that extracellular ATP may operate to maintain and regulate synaptic efficacy and plasticity in conditions of abnormal intracellular ATP depletion by phosphorylation of a surface protein substrate via activation of ecto-protein kinases. [source] Intracellular fibroblast growth factor produces effects different from those of extracellular application on development of avian cochleovestibular ganglion cells in vitroJOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2003Masako M. Bilak Abstract In an avian coculture system, the neuronal precursors of the cochleovestibular ganglion typically migrated from the otocyst and differentiated in response to soluble fibroblast growth factor (FGF-2), which had free access to FGF receptors on the cell surface. Free FGF-2 switched cells from a proliferation mode to migration, accompanied by increases in process outgrowth, fasciculation, and polysialic acid expression. Microsphere-bound FGF-2 had some of the same effects, but in addition it increased proliferation and decreased fasciculation and polysialic acid. As shown by immunohistochemistry, FGF-2 that was bound to latex microspheres depleted the FGF surface receptor protein, which localized with the microspheres in the cytoplasm and nucleus. For microsphere-bound FGF-2, the surface receptor-mediated responses to FGF-2 appear to be limited and the door opened to another venue of intracellular events or an intracrine mechanism. © 2003 Wiley-Liss, Inc. [source] Regulatory volume decrease is actively modulated during the cell cycleJOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2002Liwei Wang Nasopharyngeal carcinoma cells, CNE-2Z, when swollen by 47% hypotonic solution, exhibited a regulatory volume decrease (RVD). The RVD was inhibited by extracellular applications of the chloride channel blockers tamoxifen (30 ,M; 61% inhibition), 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB, 100 ,M; 60% inhibition), and ATP (10 mM; 91% inhibition). The level and time constant of RVD varied greatly between cells. Most cells conducted an incomplete RVD, but a few had the ability to recover their volume completely. There was no obvious correlation between cell volume and RVD capacity. Flow cytometric analysis showed that highly synchronous cells were obtained by the mitotic shake-off technique and that the cells progressed through the cell cycle synchronously when incubated in culture medium. Combined application of DNA synthesis inhibitors, thymidine and hydroxyurea arrested cells at the G1/S boundary and 87% of the cells reached S phase 4 h after being released. RVD capacity changed significantly during the cell cycle progression in cells synchronized by shake-off technique. RVD capacity being at its highest in G1 phase and lowest in S phase. The RVD capacity in G1 (shake-off cells sampled after 4 h of incubation), S (obtained by chemical arrest), and M cells (selected under microscope) was 73, 33, and 58%, respectively, and the time constants were 435, 769, and 2,000 sec, respectively. We conclude that RVD capacity is actively modulated in the cell cycle and RVD may play an important role in cell cycle progress. J. Cell. Physiol. 193: 110,119, 2002. © 2002 Wiley-Liss, Inc. [source] | ||||||||||