Alterations in protein kinase A and different protein kinase C isoforms in the heart during morphine withdrawal.

The present study was designed to investigate the possible changes of protein kinase A (PKA) and different isoforms of protein kinase C (PKC): PKC alpha, PKC delta and PKC zeta after naloxone induced morphine withdrawal in the heart. Male rats were implanted with placebo (naïve) or morphine (tolerant/dependent) pellets for 7 days. On day 8 rats received saline s.c. or naloxone (5 mg/kg s.c.). The protein levels of PKA, PKC delta and PKC zeta were significantly up-regulated in the heart from morphine withdrawal rats. By contrast, morphine withdrawal induced down-regulation of PKC alpha. These results suggest that both PKA and PKC may be involved in the cardiac adaptive changes observed during morphine withdrawal.