Fig. 4

Optogenetic stimulation of ChR2-expressing NAc core axonal terminals in the VP evoked a SWS response. a A_2AR-Cre mice were injected with AAV-EF1α-DIO-ChR2-mCherry into the NAc core and photostimulation occurred at the target side, e.g., the VP. b Typical cell-attached recording of a VP neuron in a NAc-ChR2 mouse. Brief light pulses decreased the firing rate. c Optical stimulations elicited IPSC in a VP neuron (measured in voltage-clamp at –70 mV). The individual trace is shown in grey, whereas the averaged trace is shown in black. d Optogenetically evoked IPSC were completely blocked in the presence of picrotoxin (PTX: 100 μM; shown in pink). e Number and proportion of neurons in the VP, LH, VTA and TMN that responded to optical stimulation of ChR2-expressing NAc terminals. f Typical examples of EEG, EMG and hypnograms of a NAc-ChR2 mouse, in which photostimulation of ChR2-expressing NAc terminals in the VP induced SWS (bottom panel), as compared to baseline sleep in a mouse without photostimulation (top panel). g Hourly amount of SWS during optogenetic stimulation. Only photostimulation of terminals in the VP induced SWS in NAc-ChR2 mice. h Sequential brain sections of a VP-lesioned NAc-ChR2 mouse stained with neuronal marker NeuN (left panel) and mCherry (right panel) show neuronal cell loss in the VP portion, while this area is innervated by ChR2/mCherry-expressing NAc core terminals. Scale bars: 500 μm. i Hourly amount of SWS during VP photostimulation in VP-lesioned NAc-ChR2 mice. Data are presented as the mean ± SEM. Each pair of grey dots indicates data from one mouse. **P < 0.01 compared to baseline sleep of NAc-ChR2 mice without photostimulation, assessed by paired two-tailed Student’s t-test (g, i). Blue bars indicate the period of light illumination. Other abbreviation: OT, olfactory tubercle; ac, anterior commissure; 3 V, third ventricle. N.S., not significant