Activation of striatal dopaminergic grafts by haloperidol.

The effect of haloperidol (0.5 mg/kg, 60 min) on striatal dopamine metabolism of intact rats and of rats bearing a dopaminergic graft implanted into the previously denervated striatum was investigated. The dopaminergic grafts increased dopamine and dihydroxyphenylacetic acetic acid (DOPAC) contents to 6.2 and 9.6% of their respective control levels (lesioned striatum: 0.5 and 0.7% respectively). Haloperidol increased both the DOPAC content and the DOPAC:DA ratio in the grafted striatum, and the magnitude of these increases were similar to those seen in intact controls. Furthermore a tendency for the high striatal DOPAC:DA ratio seen in lesioned striata to revert toward control values could also be observed in grafted animals. The significance of these results is discussed in terms of the in vivo regulation of graft activity.