Comparison by microdialysis of striatal L-DOPA after its systemic administration in rats with probes implanted acutely or through a guide cannula

Different methods of microdialysis probe implantation are utilized accordin g to the purpose and needs of each particular study. However, very few expe riments have systematically examined whether these different techniques hav e an impact on the obtained data. In the present study we examined the infl uence of two different microdialysis methods - acute probe implantation vs. insertion into a preimplanted guide cannula - on the striatal extracellula r availability of systemically administered L-DOPA. Furthermore, we monitor ed the effects of L-DOPA administration on dopamine and its metabolite 3,4- dihydroxyphenylacetic acid (DOPAC). In rats that received a guide cannula 4 days prior to probe insertion and microdialysis, extracellular L-DOPA conc entrations increased to concentrations that were about nine times higher th an in rats with acute implantation of a microdialysis probe. Extracellular DOPAC concentrations were also higher in the chronic preparations but dopam ine concentrations showed no differences between groups. Our results sugges t that the observed differences may be due to inflammatory disruption of th e BBB following chronic implantation of a guide cannula. (C) 2000 Elsevier Science B.V. All rights reserved.