Our previous studies showed that spinal neurons sensitization was involved in
morphine withdrawal response. This study was to investigate the roles of spinal
protein kinase C (PKC) alpha, gamma in
morphine dependence and
naloxone-precipitated withdrawal response. To set up
morphine dependence model, rats were subcutaneously injected with
morphine (twice a day, for 5 d). The dose of
morphine was 10 mg/kg in the first day and was increased by 10 mg/kg each day. On day 6, 4 h after the injection of
morphine (50 mg/kg),
morphine withdrawal syndrome was precipitated by an injection of
naloxone (4 mg/kg, i.p.).
Chelerythrine chloride (CHE), a PKC inhibitor, was intrathecally injected 30 min before the administration of
naloxone. The scores of
morphine withdrawal symptom and
morphine withdrawal-induced
allodynia were observed. One hour after
naloxone-precipitated withdrawal, Fos
protein expression was assessed by immunohistochemical analysis and Western blot was used to detect the expression of cytosol and membrane fraction of PKC alpha and gamma in the rat spinal cord. The results showed that intrathecal administration of CHE decreased the scores of
morphine withdrawal, attenuated
morphine withdrawal-induced
allodynia and also inhibited the increase of Fos
protein expression in the spinal cord of
morphine withdrawal rats. The expression of cytosol and membrane fraction of PKC alpha was significantly increased in the spinal cord of rats with
morphine dependence.
Naloxone-precipitated withdrawal induced PKC alpha translocation from cytosol to membrane fraction, which was prevented by intrathecal administration of CHE. During
morphine dependence, but not
naloxone-precipitated withdrawal,
PKC gamma in the spinal cord translocated from cytosol to membrane fraction, and intrathecal administration of CHE did not change the expression of
PKC gamma in the spinal cord of
naloxone-precipitated withdrawal rats. It is suggested that up-regulation and translocation of PKC in the spinal cord contribute to
morphine dependence and
naloxone-precipitated withdrawal in rats and that PKC alpha and gamma play different roles in the above-mentioned effect.