An immunocytochemical study of intraneuronal inclusions of the caudate and substantia nigra. Reaction with an anti-actin antiserum.

The composition of the eosinophilic inclusions of the large neurons in the human caudate nucleus and of neurons in the substantia nigra was investigated by immunocytochemical methods. Sections of caudate nucleus and substantia nigra were stained using a peroxidase-anti-peroxidase method with antisera to actin, to neurofilament proteins, and to a crude CNS microtubule fraction, the last of which reacts with neurofibrillary tangles. Of the several antisera, only the anti-actin antiserum gave positive results, indicating that these inclusions, composed of regularly arranged filaments, are highly ordered aggregates of actin polymers.