Comparative studies of D_2 receptors and cerebral blood flow in hemi-Parkinsonism rats

Objective To study the relationship between dopamine D 2 receptors and cerebral blood flow in hemi Parkinsonism rats Methods Hemi Parkinsonism rats were made by stereotaxic 6 hydroxy dopamine (6 OH DA) lesions in substantia nigra and ventral tegmental area, apomorphine (Apo) which could induce the successful model rat to rotate toward the intact side was used to select the rat models, 125 I IBZM in vivo autoradiography and 99 Tc m HMPAO regional cerebral biodistribution analysis were used to study D 2 receptors and cerebral blood flow The HPLC ECD was used to measure striatum DA and its metabolite content Results The lesioned side striatum DA and its metabolites homovanillic acid (HVA) 3,4 dihydroxyphenylacetic acid (DOPAC) reduced significantly than that of the intact side and pseudo operated group, striatum/cerebellum 125 I IBZM uptake ratio was 8 04±0 71 in lesioned side of hemi Parkinsonism rats, significantly increased compared with the intact side and the pseudo operated group (P0 05), (30 11±4 53)% of enhancement as compared to the intact side, and also showed good correlation with Apo induced rotation numbers within 30 min (r=0 98), the regional cerebral blood flow study didn't show significant difference between brain cortex area of lesioned side and its counterpart of the intact side (P0 05) Conclusions The 6 OH DA lesioned side DA content decreased significantly and thus induced a compensative up regulation of striatum D 2 receptor binding sites in hemi Parkinsonism rats, which show good correlation with rotation behavior induced by Apo Comparing with cerebral blood flow, D 2 receptor reflected by IBZM seems to be more specific and earlier to detect the cerebral functional impairment in experimental hemi Parkinsonism