Effects of morphine dependence and withdrawal on neurosteroids and amino acid transmitters of rat amygdala / 解放军医学杂志

ABSTRACT

Objective To investigate the effects of morphine dependence and withdrawal on neurosteroids and amino acid transmitters of rat amygdala. Methods Morphine dependence was induced by pretreatment with increasing doses of morphine for 7 days. Withdrawal was precipitated by naloxone (2mg/kg). Withdrawal syndromes were observed and scored. After decapitation, amygdala was dissected out. Nomadic and conjugated neurosteroids were extracted using liquid-liquid extraction and solid phase extraction. Concentrations of neurosteroids including dehydroepiandrosterone (DHEA), pregnenolone (PREG), allopregnanolone (AP), dehydroepiandrosterone sulfate (DHEAS) and pregnenolone sulfate (PREGS) were detected with HPLC-MS. Concentrations of glycine (GLY), glutamate (GLU) and gamma-aminobutyric acid (GABA) were quantitated by HPLC-ECD with pre-column OPA derivatization. Results Compared with saline control, the DHEA level in rat amygdala of morphine dependent group decreased by 33% (P＜0.01). Compared with naloxone control, the PREG and AP levels in rat amygdala of morphine withdrawal group increased by 45% (P＜0.05) and 42% (P＜0.05) respectively; the GABA level decreased by 18% (P＜0.01). Compared with morphine dependent group, the PREG and PREGS levels in rat amygdala of morphine withdrawal group increased by 60% and 40% respectively (P＜0.05); the glycine level decreased by 14% (P＜0.05). Conclusion The DHEA in rat amygdala may play a role in the development of morphine dependence but not involved in the manifestation of withdrawal symptoms. Other neurosteroids (including PREG, AP and PREGS) in rat amygdala seem to be involved in withdrawal but not in dependence. The synthesis and release of inhibitory amino acids in amygdala were depressed when withdrawal was precipitated by naloxone. The results suggest that different changes of neurosteroids and amino acids exist in stages of morphine dependence and withdrawal.