The PKs PKA and ERK 1/2 are involved in phosphorylation of TH at Serine 40 and 31 during morphine withdrawal in rat hearts.
OBJECTIVE
Our previous studies have shown that morphine withdrawal induced hyperactivity of cardiac noradrenergic pathways. The purpose of the present study was to evaluate the effects of morphine withdrawal on site-specific phosphorylation of TH in the heart.


METHODS
Dependence on morphine was induced by a 7-day s.c. implantation of morphine pellets in rats. Morphine withdrawal was precipitated on day 8 by an injection of naloxone (2 mg kg(-1)). TH phosphorylation was determined by quantitative blot immunolabelling using phosphorylation state-specific antibodies.


RESULTS
Naloxone-induced morphine withdrawal induced phosphorylation of TH at serine (Ser)40 and Ser31 in the right ventricle, associated with both an increase in total TH levels and an enhancement of TH activity. When HA-1004 (PK A inhibitor) was infused, concomitantly with morphine, it diminished the increase in noradrenaline turnover, total TH levels and TH phosphorylation at Ser40 in morphine-withdrawn rats. In contrast, the infusion of calphostin C (PKC inhibitor), did not modify the morphine withdrawal-induced increase in noradrenaline turnover and total TH levels. In addition, we show that the ability of morphine withdrawal to stimulate phosphorylation at Ser31 was reduced by SL327, an inhibitor of ERK 1/2 activation.


CONCLUSIONS
The present findings demonstrate that the enhancement of total TH levels and the increased phosphorylation state of TH during morphine withdrawal were dependent on PKA and ERK activities and suggest that these transduction pathways might contribute to the activation of the cardiac catecholaminergic neurons in response to morphine withdrawal.
Almela
P
P
Department of Pharmacology, University School of Medicine, Murcia University, Murcia, Spain.
Milanés
Mv
M
Laorden
Ml
M
D000607:Aminoacetonitrile / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004195:Disease Models, Animal; D004343:Drug Implants; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009020:Morphine / Q000008:administration & dosage*; D009021:Morphine Dependence / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology*; D009270:Naloxone; D009281:Naphthalenes / Q000378:metabolism; D009292:Narcotic Antagonists; D009638:Norepinephrine / Q000378:metabolism; D010766:Phosphorylation; D051745:Protein Kinase C-delta / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012694:Serine; D013375:Substance Withdrawal Syndrome / Q000201:enzymology* / Q000209:etiology; D013449:Sulfonamides / Q000494:pharmacology; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
D004343:Drug Implants; D007546:Isoquinolines; D009281:Naphthalenes; D009292:Narcotic Antagonists; D047428:Protein Kinase Inhibitors; C424127:SL 327; D013449:Sulfonamides; D009270:Naloxone; D000607:Aminoacetonitrile; D012694:Serine; D009020:Morphine; C043204:N-(2-guanidinoethyl)-5-isoquinolinesulfonamide; D014446:Tyrosine 3-Monooxygenase; D017868:Cyclic AMP-Dependent Protein Kinases; D051745:Protein Kinase C-delta; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C058819:calphostin C; D009638:Norepinephrine