Cocaine-sensitive O-methylation of noradrenaline in dental pulp of the rabbit: Comparison with the rabbit ear artery |
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Authors: | D A S Parker I S de la Lande C Proctor V Marino N X Lam I Parker |
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Institution: | (1) Departments of Dentistry, The University of Adelaide, G.P.O. Box 498, 5000 Adelaide, South Australia, Australia;(2) Departments of Dentistry, Clinical and Experimental Pharmacology, The University of Adelaide, G.P.O. Box 498, 5000 Adelaide, South Australia, Australia |
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Abstract: | Summary Incisor pulp from the rabbit metabolises exogenous noradrenaline in concentrations between 0.12 and 1.2 mol/l mainly to NMN.Effects of chronic sympathetic denervation indicated that in incisor pulp the NMN is extraneuronal in origin, and that DOPEG and DOMA formation, as well as a major part of the noradrenaline which accumulates in the tissue, are associated with the sympathetic nerves.NMN formation was unaffected by hydrocortisone 210 mol/l, but was strongly inhibited by cocaine 30 mol/l. These effects contrasted with those in the rabbit ear artery, where NMN formation was increased by cocaine 30 mol/l and decreased by hydrocortisone 210 mol/l.In COMT-inhibited denervated pulp, cocaine inhibited the accumulation of noradrenaline.Monoamine fluorescence histochemistry of pulp exposed to noradrenaline 50 mol/l indicated that cocaine-sensitive uptake occurred in fibroblasts.It is concluded that O-methylation of noradrenaline in dental pulp involves prior uptake of the amine by a process resembling uptake, but which is distinguished from uptake1 by its extraneuronal location.Abbreviations DOMA
3,4-dihydroxy mandelic acid
- DOPEG
3,4-dihydroxyphenylethyleneglycol
- NMN
normetanephrine
- OMDA
O-methyl deaminated metabolite fraction, comprising vanillyl-mandelic acid (VMA) plus the 3-methoxy derivative of DOPEG (MOPEG)
- MAO
monoamine oxidase
- COMT
catecholO-methyl transferase
Send offprint requests to I. S. de la Lande at the above address |
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Keywords: | Rabbit dental pulp Ear artery Noradrenaline uptake Metabolism Cocaine |
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