Nigral grafts in animal models of Parkinson's disease

Parkinson’s disease (PD) is a common neurodegenerative disorder that usually presents in middle age or early old age. It is found everywhere throughout the world, with an estimated prevalence of between 30 and 330 per 100,000 population (reviewed in Tanner & Goldman, 1996 ). The disease is characterised clinically by a picture of tremor, difficulty initiating movement (bradykinesia), and rigidity, which is due to an underlying degeneration of the pigmented dopaminergic cells of the substantia nigra (SN), the pathological appearance of Lewy bodies in the SN and elsewhere, and a severe biochemical decline in dopamine in the nigrostriatal pathway ( Agid, 1991 ; Forno, 1990 ) ( Fig. 4.1 ). The clinical picture of parkinsonism is a feature of many CNS (central nervous system) diseases involving the basal ganglia in the brain and as a result misdiagnosis of idiopathic PD is not uncommon ( Hughes et al., 1992 ). This is important because the ability accurately to diagnose true idiopathic PD is not only critical for an understanding of the aetiology of this condition, but will also be central to any transplantation programme.