Figure 2.

Inhibitory potentials and underlying currents resulting in motor thalamus from local ChR2 activation in nigral termination areas. (A) At the time indicated by 0 a 10 ms light pulse was delivered from a blue laser light source to the slice via a glass fiber. The fiber was held with a micromanipulator and the tip manually placed close to the brains slice with the light cone pointed at VM. The baseline membrane potential at the time of stimulation was controlled with a bias current injection through the recording electrode. (B) Outward currents elicited with a light pulse of varying duration between 1 and 0.2 ms in voltage clamp at −50 mV holding potential. Note that the response is graded with stimulus duration and shows multiple peaks at longer stimulus duration. Even with the shortest stimulus duration, however, failures were not observed, arguing against this ~100 pA response being carried by a single synapse. The response latency from light stimulus to IPSC onset was 3.2 ms in this neuron.