VIDEO ABSTRACT.

Neuroscience produces a vast amount of data from an enormous diversity of neurons. A neuronal classification system is essential to organize such data and the knowledge that is derived from them. Classification depends on the unequivocal identification of the features that distinguish one type of neuron from another. The problems inherent in this are particularly acute when studying cortical interneurons. To tackle this, we convened a representative group of researchers to agree on a set of terms to describe the anatomical, physiological and molecular features of GABAergic interneurons of the cerebral cortex. The resulting terminology might provide a stepping stone towards a future classification of these complex and heterogeneous cells. Consistent adoption will be important for the success of such an initiative, and we also encourage the active involvement of the broader scientific community in the dynamic evolution of this project.

The axon initial segment (AIS) of pyramidal cells is a critical region for the generation of action potentials and for the control of pyramidal cell activity. Here we show that Na ؉ and K ؉ voltagegated channels, together with other molecules involved in the localization of ion channels, are distributed asymmetrically in the AIS of pyramidal cells situated in the human temporal neocortex. There is a high density of Na ؉ channels distributed along the length of the AIS together with the associated proteins spectrin ␤IV and ankyrin G. In contrast, Kv1.2 channels are associated with the adhesion molecule Caspr2, and they are mostly localized to the distal region of the AIS. In general, the distal region of the AIS is targeted by the GABAergic axon terminals of chandelier cells, whereas the proximal region is innervated, mostly by other types of GABAergic interneurons. We suggest that this molecular segregation and the consequent regional specialization of the GABAergic input to the AIS of pyramidal cells may have important functional implications for the control of pyramidal cell activity.inhibition ͉ interneurons ͉ neocortex