Relationship of 5-hydroxy indole acetic acid, melatonin and dopamine in rat model of Parkinson’s disease induced by 6-hydroxydopamine

Abstract

Objective To investigate dynamic changes in extracellular striatal 5-hydroxy indole acetic acid (5-HIAA) and melatonin (MLT) concentrations in the 6-hydroxydopamine (6-OHDA)-induced Parkinson’s disease (PD) rat models. Methods A hemiparkinsonium rat model was established by a unilateral injection of 6-OHDA into the right substantia nigra pars compacta (SNc) and the right medial forebrain bundle (MFB). Dialysate samples were collected at 10: 00 in the lesioned striatum by microdialysis at 1, 2, 3 and 4 weeks post-lesion, respectively. The levels of dopamine (DA) and 5-HIAA, as well as MLT in dialysate samples were measured by high performance liquid chromotorgraphy (HPLC). Results One week after surgery, the level of DA in PD group was (1.19±0.22) ng/ml, which was distinctly lower than those in the vehicle group ((8.62±0.73) ng/ml) and the sham group ((8.73±0.78) ng/ml) (P<0.01). The levels of 5-HIAA in PD group had a downward trend, but there were no significant differences. The level of MLT in PD group was (43.31±11.37)pg/ml at 4 weeks post-lesion, and significantly higher than those in the vehicle group ((19.13±5.38)pg/ml) and the sham group ((19.80±6.96)pg/ml) (P<0.05). The striatal dialysate DA and 5-HIAA concentrations had a good positive correlation in the PD group (r=0.867, P<0.01). Conclusion Decreased DA level concomitantly with changes of 5-HIAA and MLT in the ipsilateral striatum of 6-OHDA-induced PD rats, and these changes may be related to PD progression. Key words: Parkinson’s disease; Dopamine; 5-hydroxy indole acetic acid; Melatonin