[Synaptic contacts in schizophrenia: study with immunocytochemical identification of dopaminergic neurons]

Immunocytochemical identification of dopaminergic neurons was made by means of immunoperoxidase method using antibodies to tyrosine hydroxylase. The ultrastructure of synaptic contacts located on dopaminergic (tyrosine hydroxylase immunopositive--TP) neurons was investigated in substantia nigra (SN) of postmortem brains in 4 schizophrenic patients compared to 3 mentally healthy control cases. Various alterations of ultrastructure have been found in presynaptic terminals which contracted with TP neurons in SN of schizophrenic patients as compared to the control group. These alterations included: presynaptic axon terminals decreased in sizes with dense matrix and density packed vesicles; swollen terminals with clustering of synaptic vesicles and displaced active zone of synapse; hyperplasia of mitochondria in the part of presynaptic boutons; appearance of abnormal membranous lamellar structures inside or outside presynaptic boutons. The altered presynaptic terminals were preferentially located on distal (small and middle diameter) TP dendrites in pars compacta of SN, where practically all dendrites revealed belonged to dopaminergic neurons and formed asymmetric contacts with short active zones in most cases. The changes of ultrastructure of synaptic contacts could be rarely observed in SN pars reticulata of schizophrenic patients both on TP and tyrosine hydroxylase immunonegative dendrites presented here.