Phorbol ester enhances excitatory amino acid-induced dopamine release from mesencephalic cell cultures.
The hypothesis that protein kinase C activation can modulate excitatory amino acid-induced dopamine release was tested by investigating effects of phorbol esters, direct activators of protein kinase C, on dopamine release stimulated by N-methyl-D-aspartate (NMDA) and non-NMDA sub-types of excitatory amino acid agonists in fetal rat mesencephalic cell cultures. The phorbol ester, 12-O-tetradecanoyl phorbol-13-acetate (TPA), enhanced dopamine release evoked by NMDA, kainate, quisqualate and by K+ depolarization. Release in the presence of NMDA and TPA was completely abolished by the NMDA antagonist, MK-801. TPA enhancement of NMDA-stimulated dopamine release was likely due to protein kinase C activation by the phorbol ester since (1) the NMDA response was enhanced by nanomolar concentrations of TPA, (2) two phorbol esters capable of activating protein kinase C enhanced the NMDA response while an inactive phorbol ester did not, (3) staurosporine, a potent protein kinase C inhibitor, blocked TPA enhancement of the NMDA response. TPA enhancement of NMDA-stimulated dopamine release was not blocked by H8, an inhibitor with high affinity for cyclic nucleotide dependent kinases, while forskolin, a direct activator of adenylate cyclase, had no effect on NMDA-stimulated release, indicating a lack of involvement of cAMP-dependent kinase in the TPA effect. TPA enhanced NMDA-stimulated release both in the presence and absence of Mg2+, indicating that TPA enhancement was not due to reversal of a Mg2+ blockade of the NMDA receptor.(ABSTRACT TRUNCATED AT 250 WORDS)
Boksa
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Douglas Hospital Research Centre, Department of Psychiatry, McGill University, Montreal, Que., Canada.
Mount
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Chaudieu
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D000596:Amino Acids / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D004298:Dopamine / Q000378:metabolism*; D008636:Mesencephalon / Q000187:drug effects* / Q000196:embryology / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology*; D051381:Rats; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects*; D017981:Receptors, Neurotransmitter / Q000187:drug effects*
D000596:Amino Acids; D004298:Dopamine; D010703:Phorbol Esters; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter