The development of dopamine overflow from foetal nigral grafts in the intact rat striatum and their influence on contralateral striatal dopamine overflow

In this study, cell suspensions of foetal rat ventral mesencephalic, dopami nergic tissue were grafted to the intact (non-lesioned) striatum of adult r ats. Differential pulse voltammetry at carbon-fibre micro electrodes (12 mu m diameter) was employed to first, monitor the development of dopamine over flow over a 20 week period within the grafts and secondly, their influence on contralateral striatal dopamine overflow. At 8 and 20 weeks, animals wer e pre-treated with pargyline and both striata were monitored for dopamine o verflow for 90 min following d-amphetamine administration. Amphetamine led to a significant increase in dopamine overflow in both the grafted striatum and the contralateral striatum. The time course of dopamine overflow in bo th the grafted striatum and the striatum contralateral to the graft was sim ilar in all groups of animals. Although the actual concentration of dopamin e measured in 20 week old grafts was more (approximate to 21%) than that me asured in 8 week old grafts, there was no significant difference between th e two time points. The concentration of dopamine measured in the striatum c ontralateral to 8 week old grafts was significantly lower (approximate to 4 3%) than that measured in the striatum of a normal control rats. There was no significant difference between the concentration of dopamine measured in the striatum contralateral to 20 week old grafts and normal control rats. In conclusion, dopamine overflow from a ventral mesencephalic graft does no t change significantly between 8 and 20 weeks following grafting. However, the grafted tissue causes a decrease of d-amphetamine-induced dopamine over flow in the contralateral side 8 weeks following grafting, which is restore d 12 weeks later. (C) 2001 Elsevier Science Ltd. All rights reserved.