RESUMEN
Microdialysis technique in free-moving animals can be used to monitor continuously the changes of many extracellular neurotransmitters in certain brain areas and study the relationship between neurotransmitter and functions. Using detection of capillary electrophoresis combined with laser-induced fluorescence (CE-LIF) further improves the above-mentioned technique. In the present study, fluorescein isothiocyanate (FITC) was used to derivatizate amino acid in very low concentration. We found that increasing derivatization temperature could shorten derivatization time and that the derivatizative efficiency was not different from that when experiment was performed under the traditional derivatization condition (room temperature for 16 h). We also got an optimized condition of amino acid derivatization with FITC at 30 degrees C water bath for 5 h. Using the optimized condition of amino acid derivatization, we investigated the changes in L-arginine (L-Arg) and L-glutamate (L-Glu) concentration in periaqueductal gray matter (PAG) microdialytes of free-moving morphine-withdrawal rats. The results indicated that there was no significant difference in the concentration of L-Arg and L-Glu in PAG between non-dependent and dependent rats. The concentration of L-Arg and L-Glu in PAG increased by 63% and 105%, respectively, in the first 10 min after naloxone-precipitated withdrawal and then declined gradually. These changes were in correspondence with the scores of morphine withdrawal symptom.