[The expression of glial cell derived neurotrophic factor and its receptor GDNFR-alpha and GDNFR-beta mRNA in spinal cord, brainstem and frontal cortex during morphine withdrawal in rats].

OBJECTIVE

To investigate the expression of glial cell derived neurotrophic factor (GDNF) and its receptor GDNFR-alpha (GFRalpha-1) and GDNFR-beta (Ret) genes and the effects of muscarinic receptor antagonists, NMDA receptor antagonist, inhibitor of nitric oxide synthase on the expression of these genes in the spinal cord, brainstem and frontal cortex during morphine withdrawal, and to observe the effects of GDNF antisense oligoneucleotide (i.c.v) on the morphine withdrawal symptoms in rats.

METHODS

The levels of GDNF, GDNFR-alpha and GDNFR-beta mRNA were assayed by reverse transcription polymerase chain reaction (RT-PCR) with the beta-actin mRNA as an internal control.

RESULTS

The GDNF mRNA levels were increased, and GDNFR-alpha and GDNFR-beta mRNA levels was slightly increased in the spinal cord and brainstem during morphine dependence. These genes were decreased at 1 h, increased at 2 h after administration of naloxone in morphine dependent rats. While the GDNF, GDNFR-alpha and GDNFR-beta levels in the frontal cortex were increased significantly at 1, 2 and 4 h after the injection of naloxone during morphine withdrawal. The pre-treatment with L-N-nitric arginine methylester (10 mg/kg), the expressions of GDNF and GDNFR-beta in the spinal cord, both GDNFR-alpha and GDNFR-beta in the frontal cortex were decreased. The expressions of both GDNF and GDNFR-alpha in the frontal cortex were decreased by treatment with MK801 (0.5 mg/kg), and the expressions of GDNF in both the stem and cortex, and GDNFR-beta in the brainstem decreased by treatment with the methyl-scopolamine (0.5 mg/kg). The beta-actin mRNA levels were not different in each group. Moreover, the morphine withdrawal symptoms were attenuated by intracerebroven tricular injection of GDNF antisense oligoneucleotide in 6 hour and 24 hour before naloxone administration in morphine dependent rats.

CONCLUSION

The results not only provide direct evidence that the expressions of GDNF and its receptors mRNA in glial cells play an important role in mediating the process of morphine dependence and may be account for the long-term neuro-adaptation associated with morphine dependence, but also suggest that muscarinic receptor, NMDA receptor and nitric oxide pathways may be involved in the expression of GDNF and GDNF receptor genes during morphine withdrawal.