Antagonistic effects of dopaminergic signaling and ethanol on protein kinase A-mediated phosphorylation of DARPP-32 and the NR1 subunit of the NMDA receptor.
BACKGROUND
This article extends our initial investigation of the interactions between dopamine and glutamate receptor systems after acute exposure to ethanol. DARPP-32 (dopamine and cyclic adenosine monophosphate-regulated phosphoprotein of approximate molecular weight 32 kDa) is an important regulator of protein phosphatase-1 that in turn regulates a large number of effectors, including the NMDA receptor.


METHODS
We measured the protein kinase A (PKA)-mediated phosphorylation of DARPP-32 and the NR1 subunit of the NMDA receptor. Initially, corpus striatum was assayed after intraperitoneal treatment of mice with the D1 agonist SKF82958, the D2 agonist and anticraving drug bromocriptine, or ethanol. In other experiments we blocked D1 receptors with the selective D1 antagonist SCH23390 or blocked D2 receptors with the selective D2 antagonist eticlopride. Finally, we examined combinations of some dopaminergic drugs with and without ethanol.


RESULTS
SKF82958 alone significantly increased PKA-mediated phosphorylation of both DARPP-32 and NR1. Bromocriptine alone had no effect on pDARPP-32 or on pNR1. However, when D1 receptors were blocked, bromocriptine reduced the PKA-mediated phosphorylation of both DARPP-32 and NR1. Coincident treatment with bromocriptine and ethanol reversed both of these effects with D1 receptors blocked. The combination of eticlopride (D2 blocker) and SF82958 (D1 agonist) did not significantly alter either pDARPP-32 or pNR1.


CONCLUSIONS
These data demonstrate antagonistic effects of acute ethanol exposure on D1 signaling in vivo and the potential of acute in vivo challenge protocols to help fill gaps in the understanding of ethanol's effects on protein phosphorylation.
Edwards
Scott
S
Department of Psychiatry and Center for Basic Neuroscience, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA.
Simmons
Diana L
DL
Galindo
David G
DG
Doherty
James M
JM
Scott
Anne M
AM
Hughes
Peter D
PD
Wilcox
Richard E
RE
D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D001971:Bromocriptine / Q000494:pharmacology; D003342:Corpus Striatum / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004298:Dopamine / Q000502:physiology*; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D000431:Ethanol / Q000494:pharmacology*; D008297:Male; D051379:Mice; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D012457:Salicylamides / Q000494:pharmacology; D015398:Signal Transduction
D001552:Benzazepines; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D016194:Receptors, N-Methyl-D-Aspartate; D012457:Salicylamides; D001971:Bromocriptine; D000431:Ethanol; C071262:SK&F 82958; D017868:Cyclic AMP-Dependent Protein Kinases; C045989:eticlopride; D004298:Dopamine