Figure 8.

Photostimulation of serotonergic axons expressing ChR2 increases spike firing in fusiform cells. A, Sustained photostimulation (blue light pulse with 5 ms duration) elicited an inward current. Top trace, An inward current evoked by a 30 s train of light pulses at 100 Hz. Bottom trace, This current was blocked by 10 μm ketanserin. B, Pooled data show photostimulation-evoked currents were largely blocked by ketanserin (n = 4). C, Example traces from a fusiform cell show that tetanic photostimulation increases the firing rate. D, Representative traces of action potential firing elicited by somatic injection of current pulses (−10, 10, 30, and 50 pA, 1 s duration) illustrating the effects of photostimulation of serotonergic fibers. E, Pooled data show photostimulation of serotonergic fibers significantly increase the firing rate at 10 or 30 pA depolarizing steps (n = 5).