Figure 4 |. Behavioural transitions induced by photostimulation are mediated by Hcrt.

a, b, Effect of the Hcrt receptor 1 antagonist SB334867 (ref. 24) on latencies of light-induced wake events during SWS (a) and REM sleep (b) in Hcrt::ChR2-mCherry transduced animals (n = 3) and their controls (n = 3) after single bouts of 20 Hz photostimulation (15 ms, 10 s). Data analysis is based on an average of ten and three stimulations per frequency and per mouse for SWS and REM sleep, respectively. At the doses tested here, SB334867 had no effect on the latency of SWS and REM sleep-to-wake transitions after photostimulation in Hcrt::mCherry control animals. Latencies are represented as mean ± s.e.m. Asterisk, P<0.05 using a paired Student’s t-test between saline and drug conditions. c, Latencies of SWS sleep-to-wake transitions of Hcrt knockout (KO) animals compared with our control data; three independent mice were transduced with Hcrt::ChR2-mCherry lentiviruses and received a single photostimulation bout spanning the relevant frequencies (1–30 Hz, 15-ms light pulses, during 10 s). Hcrt knockout data analysis is based on an average of 20 stimulations at different frequencies (1–30 Hz) per mouse during SWS. Latencies are represented as pooled mean ± s.e.m. values. Triple asterisk, P<0.0001, indicates the significant difference between control mCherry and ChR2 animals using a two-tailed Student’s t-test. Asterisk, P<0.05, indicates significant difference using a two-tailed Student’s t-test between ChR2 and Hcrt knockout ChR2 animals. No significant differences in latencies to wakefulness were found between control mCherry and Hcrt knockout ChR2 animals.