Reciprocal ion channels in striatal LTS interneurons

The striatum is comprised of several interneurons, including the fast-spiking, cholinergic and LTS interneurons. These three interneuron types have sensitivity for different frequencies of input, expressed as a membrane and spiking resonance. Specifically, LTS interneurons express a membrane resonance between 7 and 14 Hz and a spiking resonance between 15 and 20 Hz. Focusing on LTS interneurons, I determined the mechanism for its membrane resonance. I hypothesized that this mechanism also drives the membrane oscillations seen in the presence of tetrodotoxin. My experiments show that L- and N-type calcium currents engage calcium-activated chloride channels to generate the membrane potential oscillations and membrane resonance. This was not the same mechanism that generates the spiking resonance. Blockade of the membrane resonance mechanism increased the strength and selectivity of the spiking resonance. These channels also increase the regularity of firing in the LTS interneuron. L-, N-type calcium and CaCCs act reciprocally to create the membrane potential oscillation, membrane resonance and add to the regularity in spiking by creating the medium AHP in striatal LTS interneurons. This mechanism combines with the spiking resonance mechanism to allow the neuron to respond to a broadband of input frequencies. The experiments were performed using perforated-patch or cell-attached recordings on sagittal slices of mouse brains. Transgenic mice that expressed green fluorescent protein under the control of the neuropeptide Y promoter were used to identify LTS cells in slice.