EXCITOTOXIC LESIONS OF THE PEDUNCULOPONTINE TEGMENTAL NUCLEUS PRODUCECONTRALATERAL HEMIPARKINSONISM IN THE MONKEY

Dopaminergic nigrostriatal neurons, degeneration of which causes Parki nson's disease, are known to receive excitatory input almost exclusive ly from the pedunculopontine tegmental nucleus (PPN). We report here t hat excitotoxic lesions of the PPN produce abnormal motor signs releva nt to hemiparkinsonism in the macaque monkey. Under the guidance of ex tracellular unit recordings, the electrophysiologically identified PPN was injected unilaterally with kainic acid. These PPN-lesioned monkey s exhibited mild to moderate levels of flexed posture and hypokinesia in the upper and lower limbs contralateral to the lesion. In most of t he monkeys, such pathophysiological events were gradually improved and became stationary in 1-2 weeks. The hemiparkinsonian symptoms observe d after PPN destruction might be ascribed to a decrease in nigrostriat al neuron activity due to excitatory input ablation. (C) 1997 Elsevier Science Ltd.