Methionine-enkephalin, substance P, and homovanillic acid in the CSF of parkinsonian patients.

Methionine-enkephalin, substance P, and homovanillic acid concentrations were measured in the CSF of subjects not affected by neurologic disorders (group 1), and in parkinsonian patients who had a slight or moderate (group 2) or severe (group 3) disability. Homovanillic acid and substance P concentrations in the CSF of groups 2 and 3 were respectively lower and higher than in group 1. On the contrary, an increase in CSF methionine-enkephalin content was found only in group 2. Our results confirm in humans the close relation between the dopaminergic and peptidergic transmissions in the nigrostriatal system that has been observed in experimental animals.