Monoclonal antibodies to the turtle cortex reveal neuronal subsets, antigenic cross-reactivity with the mammalian neocortex, and forebrain structures sharing a pallial derivation.

The dorsal cortex of the pond turtle (Pseudemys scripta) is a relatively simple structure consisting of two principal classes of neurons that occupy three distinct layers. Morphological, pharmacological, and physiological data suggest many similarities to the mammalian neocortex, rendering it an interesting preparation for comparative studies. We prepared monoclonal antibodies to the turtle dorsal cortex by immunizing mice with cortical tissue from adult turtles. Twelve antibodies were generated that recognize specific components of the turtle cortex. Among these, eight antibodies label only neurons and four label only ependymal glial cells. Differences in tissue staining pattern and immunoglobulin class suggest a heterogeneity of antigenic specificity among the antibodies. The staining patterns of three of our antibodies are described. TC3, like all other neuron-marking antibodies generated, labels a subset of both pyramidal and stellate cell types. It also cross-reacts with a subset of mammalian cortical neurons and labels them with a pattern similar to that observed in the turtle cortex. TC5 stains ependymal cells and their glial processes in the turtle cortex, and cross-reacts with fibrous astrocytelike processes in mammalian neocortical white matter. TC9 appears to recognize antigens of neurons sharing a pallial derivation in turtle.