Neurochemical and cellular specializations in the mammalian neocortex reflect phylogenetic relationships: Evidence from primates, cetaceans, and artiodactyls

Most of the available data on the cytoarchitecture of the cerebral cortex i n mammals rely on Nissl, Golgi, and myelin stains and few studies have expl ored the differential morphologic and neurochemical phenotypes of neuronal populations. in addition, the majority of studies addressing the distributi on and morphology of identified neuronal subtypes have been performed in co mmon laboratory animals such as the rat, mouse, cat, and macaque monkey, as well as in postmortem analyses in humans. Several neuronal markers, such a s neurotransmitters or structural proteins, display a restricted cellular d istribution in the mammalian brain, and recently, certain cytoskeletal prot eins and calcium-binding proteins have emerged as reliable markers for morp hologically distinct subpopulations of neurons in a large number of mammali an species. In this article, we review the morphologic characteristics and distribution of three calcium-binding proteins, parvalbumin, calbindin, and calretinin, and of the neurofilament protein triplet, a component of the n euronal cytoskeleton, to provide an overview of the presence and cellular t ypology of these proteins in the neocortex of various mammalian taxa. Consi dering the remarkable diversity in gross morphological patterns and neurona l organization that occurred during the evolution of mammalian neocortex, t he distribution of these neurochemical markers may help define taxon-specif ic patterns. In turn, such patterns can be used as reliable phylogenetic tr aits to assess the degree to which neurochemical specialization of neurons, as well as their regional and laminar distribution in the neocortex, repre sent derived or ancestral features, and differ in certain taxa from the lab oratory species that are most commonly studied. Copyright (C) 2000 S. Karge r AG. Basel.