Calcium-binding protein phenotype defines metabolically distinct groups of neurons in barrel cortex of behaving...

Physiological/anatomical studies of rat frontal cortex in vitro have distinguished subpopulations of gamma-aminobutyric acid (GABA)-expressing inhibitory interneurons defined by expression of the calcium-binding proteins, parvalbumin (PV) and calbindin (CA). Using a novel 2DG/immunostaining technique to double-label hamster barrel cortex for metabolism and phenotype, we have recently shown that while many GABAergic neurons are heavily 2DG labeled during normal exploratory behavior, a subset of GABAergic cells shows relatively sparse 2DG labeling. For this study we used the 2DG/immunostaining technique to test whether, in awake behaving animals, calcium-binding protein expression in a given cell in barrel cortex (as indicated by immunohistochemistry for PV or CA) was related to the degree of 2DG labeling. We found that most PV+ cells were moderately to heavily 2DG labeled, while most CA+ cells were lightly 2DG labeled. Our data indicate that the PV+ and CA+ cells represent metabolically distinct subpopulations of GABAergic neurons in barrel cortex. This distinction corresponds well with the in vitro physiological and anatomical data from frontal cortex and suggests functional implications for the expression of PV and CA, or other colocalized factors, in normally functioning cortical circuitry.