Intrinsic neurogenesis in the cerebral cortex continues in adult guinea pig and gives rise to new GABAergic neurons

Abstract

We have identified neuroblast‐like and immature neurons appearing to be born within the adult guinea pig cerebral cortex. Morphologically diverse cells expressing doublecortin (DCX) were confined to layer II and adjacent borders. Cells (often in clusters) varied in size, shape, label‐intensity, nuclear morphology and with somata appearing in contact with one another. DCX cells co‐expressed polysialylated neural cell adhesion molecule (PSA‐NCAM) and neuron‐specific type III beta‐tubulin. Larger DCX+ cells had well‐developed processes and expressed neuron‐specific nuclear protein (NeuN). Some DCX cells displayed reduced DCX staining but elevated NeuN expression, suggesting a transitional state of maturity. “Transitional” cells also showed immunoreactivities to GABA and GAD67. Cells expressing mitotic markers (proliferating cell nuclear antigen, Ki67, or 5‐bromo‐2′‐deoxyuridine following short survival times, were also encountered across the cortex with prevalence in layers I and II. Co‐localization of BrdU and DCX was seen in several cells following longer survival periods. Our findings suggest the superficial layers of the guinea pig cerebral cortex to be neurogenic throughout life and to provide new GABAergic neurons during adulthood. Supported by Southern Illinois University and Illinois Department of Public Health.