Figure 2. Effects of light pulse duration on ChAT-expressing interneurons of the MHB and striatum.
(A) Chat-ChR2 transgenic mice display ChR2-EYFP expression in the medial habenula (MHB) (scale bar, 1 mm) and (B) striatum (scale bar, 1 mm). Inlays show zoomed images of respective ChR2-expressing MHB or striatal interneurons (scale bars, 100 μM). Regular firing of ChR2-expressing ChAT interneurons of the (C) MHB and (D) striatum in response to brief light pulses (20 Hz, 10 ms pulse width). Prolonged light pulse duration (20 Hz, 49 ms pulse width) leads to depolarization block in (E) MHB and (F) striatal ChAT interneurons. Moderate current injection results in steady firing of ChR2-expressing (G) MHB (50 pA) and (H) striatal (80 pA) ChAT interneurons. High current injection results in depolarization block of ChR2-expressing (I) MHB (150 pA) and (J) striatal (300 pA) ChAT interneurons.