Angiotensin-converting enzyme in substantia nigra: reduction of activity in Huntington's disease and after intrastriatal kainic acid in rats.

The substantia nigra of Huntington's disease brains shows a 78% reduction in angiotensin-converting enzyme activity in the pars reticulata and a 48% reduction in the pars compacta. The nucleus accumbens shows a 28% reduction in converting enzyme activity. In the rat, after intrastriatal injections of kainic acid (2.5 microgram), an agent which selectively destroys neuronal cell bodies, there is a 55% reduction in angiotensin-converting enzyme activity in the ipsilateral substantia nigra. Both human and animal data suggest that a major part of the angiotensin-converting enzyme in the substantia nigra is localized in nerve terminals whose cell bodies originate in the striatum.