Involvement of medullary serotonergic groups in multiple system atrophy.

We sought to determine whether medullary serotonergic neurons were affected in multiple system atrophy (MSA). Immunostaining for tryptophan hydroxylase was performed on serial 50 microm sections of the medulla of brains obtained at autopsy from six control subjects, eight subjects with clinical diagnosis of MSA, and four with Parkinson's disease. There was a severe depletion of serotonergic neurons in the nucleus raphe magnus, raphe obscurus, raphe pallidus, and ventrolateral medulla in MSA. Depletion of serotonergic neurons may contribute to impaired control of sympathetic outflow and other abnormalities in MSA.