The density of pyramidal and nonpyramidal neurons in anterior cingulate cortex of schizophrenic and bipolar subjects

Background: A recent study reported a decreased density of nonpyramidal neurons (NPs) in layer II of the anterior cingulate (ACCx) and prefrontal (PFCx) cortices of schizophrenic brain that was most pronounced in schizoaffective subjects. Our study assessed whether a decrease of NPs in ACCx may show a stronger covariation with affective disorder. A cohort consisting of 12 normal control (CONs), 11 schizophrenic, and 10 bipolar subjects matched for age and postmortem interval (PMI) has been analyzed. Methods: A two-dimensional technique was employed for counting cells in a large x,y sampling column that extended across layers I through VI of ACCx. Results: There was a 27% reduction in the density of NPs in layer II of the bipolar group, whereas in the schizophrenic group, this density was 16.2% lower. There were no differences in NPs in layers III through VI of either the schizophrenic or bipolar group. Both groups also showed modest decreases of PNs in the deeper laminae; however, these differences were only significant in layer IV of the schizophrenic subjects. The density of glial cells was similar across the control, schizophrenic, and bipolar groups. An Abercrombie correction for cell size did not alter the nature of the results. Subjects both with and without neuroleptic exposure showed a lower density of NPs in layer II of bipolar subjects or PNS in deeper laminae of schizophrenic subjects. Conclusions: Overall, the findings reported here suggest that local circuit cells in layer II of ACCx may be decreased in bipolar disorder, whereas projection neurons in deeper laminae are decreased in schizophrenia. Biol Psychiatry 2001;50:395-406 (C) 2001 Society of Biological Psychiatry.