Parvalbumin neurons in the entorhinal cortex of subjects diagnosed with bipolar disorder or schizophrenia

Background: Growing evidence indicates that the entorhinal cortex (ECx) might be affected in schizophrenia (SZ) and bipolar disorder (BD). To test whether distinct interneuronal subpopulations might be altered, numbers of parvalburnin-immunoreactive (PVB-IR) neurons were measured in the ECx of BD and SZ subjects. These neurons play a pivotal role within ECx intrinsic circuits. Methods: Numbers, numerical density, and soma size of PVB-IR neurons were measured in the ECx of normal control (n = 16),BD(n = 10), and SZ (n = 10) subjects. The volume of the ECx was measured in Nissl-stained sections. Results: In 131), decreases of total numbers (p = .02) and numerical densities (p = .01) of PVB-IR neurons were detected in the ECx. Within distinct subregions, reductions were detected in the superficial layers of the lateral (p = .02), intermediate (p = .04), and caudal (p = .01) ECx. In SZ, total numbers and numerical densities were not altered. A reduction of soma size was present in the intermediate ECx (P = .01). Volume was unaffected in either disorder. Conclusions: In 131), a decrease of PVB-IR neurons may alter intrinsic inhibitory networks within the superficial layers of the ECx. The likely consequence is a disruption of integration and transfer of information from the cerebral cortex to the hippocampus.