T-type Ca2+and persistent Na+currents synergistically elevate ventral, not dorsal, entorhinal cortical stellate cell excitability

Summary The medial entorhinal cortex (mEC) plays a salient role in physiological processes such as spatial cognition and spatial coding. mEC layer II stellate neurons, in particular, influence these processes. Interestingly, ventral and dorsal stellate neurons diversely affect these processes and have distinct intrinsic membrane properties and action potential firing patterns. Little, though, is known about how ventral stellate neuron intrinsic excitability is regulated. We show that ventral stellate neurons predominantly possess T-type Ca 2+ currents encoded by Ca V 3.2 subunits, with dorsal stellate neurons having small or no currents. Further, twice as much Ca V 3.2 mRNA was present in ventral than dorsal mEC. In line with T-type, Ca V 3.2 Ca 2+ current biophysical properties, depolarising stimuli activated these currents in ventral, but not dorsal, neurons. Here, these currents acted in concert with persistent Na + currents to elevate input resistance and tonic action potential firing. Ca V 3.2 currents also enhanced excitatory post-synaptic potential decay and integration solely in ventral neurons. These results reveal that Ca V 3.2 currents, together with persistent Na + currents, impart the characteristic intrinsic membrane and firing properties of ventral stellate neurons. This signifies that specific voltage-gated conductances distinctly affect ventral and dorsal mEC stellate neuron activity and functions such as spatial memory and spatial navigation.