Figure 7. Photostimulation of PVN CRH^ChR2 neurons overrides contextual cues.

(a–d) Optical stimulation of PVN CRH neurons attenuates rearing in novel environment (Novel). (a) Each row represents an individual animal. (b) Histograms showing percentage of animals rearing. (c) Cumulative graphs demonstrate the relative extent of rearing. (d) Rearing time as a fraction of all behaviours after exclusion of time spent grooming (CRH^eYFP: 13.6±1.4%, n=10; versus CRH^ChR2: 9.2±0.9%, n=10; P=0.0165; t-test). (e–h) Optical stimulation of PVN CRH neurons disrupts freezing in FS. (e) Each row represents an individual animal. (f) Histograms show percentage of animals freezing. (g) Cumulative graphs demonstrate the relative extent of freezing. (h) Quantification of fractional freezing time if time spent grooming is excluded from the analysis (CRH^eYFP: 32.5±5.7%, n=10; versus CRH^ChR2: 15.8±3.8%, n=10; P=0.0251; t-test). (i) Assessment of locomotion in an open field test. Representative locomotor trajectory plots during optical stimulation in CRH^eYFP (black) and CRH^ChR2 (blue) mice. Accompanying graph shows CRH^ChR2 mice spend significantly less time spent in the centre zone during photostimulation (CRH^eYFP: before: 3.9±0.5%, during: 6.1±0.5%. after: 6.6±0.9, n=16; versus CRH^ChR2: before: 4.3±1.0%, during: 3.3±0.8%, after: 5.3±0.8%, n=14; CRH^eYFP during versus CRH^ChR2 during, P=0.0291; repeated-measures two-way ANOVA). (j) Representative locomotor trajectory plots during optical stimulation in CRH^eYFP (black) and CRH^ChR2 (blue) mice in a novel object (green shape) test. Optical stimulation reduces exploration of a novel object as measured by the latency to touch (k, CRH^eYFP: 127.7±36.4 s, n=6; versus CRH^ChR2: 259.0±35.2 s, n=6; P=0.0267; t-test) and the time spent in close proximity (l, CRH^eYFP: 21.2±7.6 s, n=6; versus CRH^ChR2: 3.0±2.8 s, n=6; P=0.0494; t-test). Scale bars: (b,c,f,g), 20%; *P<0.05; Error bars±s.e.m.