Substantia nigra cell death from kainic acid or folic acid injections into the pontine tegmentum.

Injections of kainic acid into the rostral pontine tegmentum in rats caused not only local lesions but destruction of GABAergic and dopaminergic cells in the substantia nigra (SN), as indicated histologically and by measurements of tyrosine hydroxylase (TH) and glutamate decarboxylase (GAD). Injections of folic acid caused the nigral damage without local lesions. Pretreatment with scopolamine prevented the losses in GAD without affecting those in TH. The destruction of nigral cells is attributed to pathological stimulation of afferent pathways to the SN, some of which are cholinergic, and it is possible that a similar mechanism may be involved in some forms of Parkinsonism.