Regulation of cyclic GMP, cyclic AMP and lactate dehydrogenase by putative neurotransmitters in the C6 rat glioma cell line (original) (raw)
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Neuroscience, 1995
The effects of the membrane-permeable cGMP analogue, 8-bromoguanosine 3':5'-cyclic monophosphate on acetylcholine-evoked catecholamine secretion and cytosolic calcium increases were studied in chromaffin cells from the bovine adrenal gland. Preincubation with 100 microM 8-bromoguanosine 3':5'-cyclic monophosphate during 10 and 30 min decreased the acetylcholine-evoked catecholamine release by 16 +/- 3% and 27 /+- 5%, respectively. The cytosolic calcium increases triggered by acetylcholine and 30 mM KCl were also inhibited by 30 min of preincubation with this compound by 27 +/- 4 and 34 /+- 12%, respectively. Changes in membrane potential induced by acetylcholine and KCl were not affected by preincubation with 8-bromoguanosine 3':5'-cyclic monophosphate. The cyclic GMP-dependent protein kinase inhibitor N-[2-(methylamino)ethyl]-5-isoquinoline sulfonamide dihydrochloride-at l micron abolished the inhibitory effect of 8-bromoguanosine 3':5'-cyclic monophosphate on acetylcholine-evoked calcium increase. By contrast, a potent and selective inhibitor against cyclic AMP-dependent protein kinase, N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide did not block the 8-bromoguanosine 3':5'-cyclic monophosphate effect. Additionally, 8-bromoguanosine 3':5'-cyclic monophosphate stimulated histone F2b phosphorylation by a partial purified cGMP-dependent protein kinase from chromaffin cells. The extent of histone phosphorylation was reduced by N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride and 8-(4-chlorophenylthio)-guanosine 3':5'-cyclic monophosphorothioate, Rp-isomer, a specific inhibitor against cyclic GMP-dependent protein kinase, whereas it was not modified by N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinoline sulfonamide. The results suggest that the inhibitory effects of 8-bromoguanosine 3':5' cyclic monophosphate on chromaffin cells are mediated through the activation of cGMP-dependent protein kinase.(ABSTRACT TRUNCATED AT 250 WORDS)
Characterization of noradrenaline-stimulated cyclic GMP formation in brain astrocytes in culture
The Biochemical journal, 1992
Cyclic GMP accumulation induced by noradrenaline in astrocyte-enriched primary cultures from rat cerebrum involves synthesis of NO, as evidenced by the competitive inhibition exerted by the NO synthase inhibitor NG-monomethyl-L-arginine (IC50 = 3 microM). Furthermore, the noradrenaline effect was potently inhibited by haemoglobin (IC50 = 25 nM) and potentiated by superoxide dismutase, indicating that NO synthesis and cyclic GMP formation may occur in different subsets of astrocytes. Investigation of the receptors implicated by using selective adrenoceptor agonists and antagonists indicates that about 75% of the NO-dependent noradrenaline response is mediated by alpha 1-adrenoceptors and the rest by beta-adrenoceptors, with no evidence for potentiating effects between the two receptor types. This noradrenaline effect appears to require Ca2+ entry, since it is strongly dependent on extracellular Ca2+ but is not affected by conditions that will abolish intracellular Ca2+ mobilization (...
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