Different methods of microdialysis probe implantation are utilized according to the purpose and needs of each particular study. However, very few experiments have systematically examined whether these different techniques have an impact on the obtained data. In the present study we examined the influence of two different microdialysis methods - acute probe implantation vs. insertion into a preimplanted guide cannula - on the striatal extracellular availability of systemically administered L-DOPA. Furthermore, we monitored 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 concentrations increased to concentrations that were about nine times higher than in rats with acute implantation of a microdialysis probe. Extracellular DOPAC concentrations were also higher in the chronic preparations but dopamine concentrations showed no differences between groups. Our results suggest that the observed differences may be due to inflammatory disruption of the BBB following chronic implantation of a guide cannula.