D-1 and D-2 dopaminergic receptors regulate protein phosphorylation in the rat neurohypophysis.
Dopamine stimulates the phosphorylation of the neuron-specific synaptic vesicle proteins Synapsin I, Protein IIIa and Protein IIIb in the posterior pituitary gland of the rat [Tsou and Greengard (1982) Proc. natn. Acad. Sci. U.S.A. 79, 6075-6079]. This effect has been characterized in the present investigation. The stimulatory effect of dopamine was mimicked by the selective D-1 receptor agonist SKF 38393 and was competitively and potently inhibited by the selective D-1 receptor antagonist SKF 83509 as well as by the mixed D-1/D-2 antagonist fluphenazine. Conversely, the effect of dopamine was attenuated by a D-2 receptor agonist (LY 141865) and potentiated by a D-2 receptor antagonist (sulpiride). Norepinephrine also stimulated phosphorylation of the synaptic vesicle proteins, apparently through activation of the D-1 receptor. D-1 and D-2 dopaminergic receptors may play a role in the regulation of hormone secretion from the neurohypophysis. Evidence exists that in the isolated neurophypophysis activation of D-1 receptors facilitates, while activation of D-2 receptors inhibits, release of vasopressin. Further work will be required to determine whether the regulation by D-1 and D-2 receptors of the protein phosphorylation in the neurohypophysial peptidergic terminals is related to the regulation by those receptors of the neurohypophysial hormone secretion.
Treiman
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M
Greengard
P
P
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000096:biosynthesis; D010766:Phosphorylation; D010904:Pituitary Gland, Posterior / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000502:physiology*; D013572:Synaptic Vesicles / Q000378:metabolism
D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D011954:Receptors, Dopamine; D015124:8-Bromo Cyclic Adenosine Monophosphate; D015056:1-Methyl-3-isobutylxanthine