Abstract
Dopamine inhibited phosphoinositide breakdown as stimulated by carbachol in rat brain cortical membranes. The IC50 value was 14 +/- 2 microM for dopamine's inhibition of phosphatidylinositol hydrolysis as stimulated by 1 mM carbachol. The inhibition was found at low (0.1 microM), but not high (greater than 0.3 microM), concentrations of the non-hydrolyzable guanine nucleotide analog, GTP gamma S. Pharmacological characterization of the response indicated that the dopamine effects were mediated by D1 receptors. The assay conditions precluded any involvement of cyclic-AMP as a mediator of the dopamine response, and thus, a novel role is proposed for dopamine in cortex working through D1 receptors to inhibit phosphoinositide degradation.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / analogs & derivatives
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2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / pharmacology
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Animals
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Benzazepines / pharmacology
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Carbachol / pharmacology
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Cerebral Cortex / drug effects
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Cerebral Cortex / metabolism*
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Dopamine / pharmacology
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Dopamine / physiology*
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In Vitro Techniques
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Male
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Phosphatidylinositols / metabolism*
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Rats
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Rats, Inbred Strains
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Receptors, Dopamine / drug effects
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Receptors, Dopamine / physiology*
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Receptors, Dopamine D1
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Receptors, Muscarinic / drug effects
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Receptors, Muscarinic / physiology*
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Type C Phospholipases / metabolism*
Substances
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Benzazepines
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Phosphatidylinositols
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Receptors, Dopamine
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Receptors, Dopamine D1
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Receptors, Muscarinic
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2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine
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Carbachol
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1H-3-benzazepin-7-ol, 8-bromo-2,3,4,5-tetrahydro-3-methyl-5-phenyl-
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Type C Phospholipases
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Dopamine