An increasing precise neuroanatomical analysis of the animal brain has been recently obtained using highly specific antibodies against various neurotransmitters. Preliminary studies of the peptidergic neurons in the basal ganglia and cerebral cortex have shown that these methods can be successfully applied to human brain. However, the dysfunction of the neural systems which may play a role in the symptomatology of Gilles de la Tourette Syndrome is still unknown. The approach chosen in this study is to search for specific alterations in neurotransmitters’ content in the post-mortem brain from patients with Gilles de la Tourette Syndrome. In a previous study, funded by Tourette Syndrome Association, we showed that the immunocytochemical localization of several chemical messengers was possible in the brain from subjects with degenerative diseases of the basal ganglia, namely Parkinson’s disease and progressive supranuclear palsy. We propose to pursue the development of this immunocytochemical approach and to extend it using cell counting methods in the brain of control subjects with parkinsonian syndromes, in order to quantify the postulated anatomo-biochemical alterations. In the future, a careful mapping of brains with Gilles de la Tourette Syndrome will be undertaken. The methods used could lead to detect deficient catecholaminergic, cholinergic peptidergic containing neuronal systems involved in the symptomatology of the disease. Should such an alteration in a chemical transmitter be identified, more effective treatments against movement disorders might be developed for patients with Tourette Syndrome, as previously achieved with the levodopa therapy for parkinsonian patients. Moreover, the discovery of a brain abnormality, either of the chemical content of the aspect of distribution of neurons, could represent the first step to approach the cause of Tourette Syndrome. Etienne Hirsch, M.D. Hôpital de La Salpetriere, Paris, France Award: $15,000 Tourette Association of America Inc. – Research Grant Award 1987