Low-threshold calcium electrogenesis in neocortical neurons.

In slices of parietal neocortex, evidence was obtained for the existence of a low-threshold Ca2+ conductance in most neurons. This conductance became apparent when resting membrane potential was held below -60 mV by continuously injected, depolarizing current. Under these conditions, brief hyperpolarizing pulses were followed by generation of tetrodotoxin (TTX)-resistant, Mn2+-sensitive, low-threshold spikes. The results suggest that in neocortex, as in many subcortical structures, low-threshold Ca current may be responsible for burst generation in some neurons.