Fig. 3: Effects of chronic social stress on behaviour and NAc DA activity in the sociosexual motivation test.

A Experimental design. BBW + FC: measurement of baseline body weight and food consumption during handling; 90–95% BBW: conditioning with sucrose as reinforcer under food restriction that reduced BW to 90-95% BBW; ♀D, conditioning with (distal) female under cup as reinforcer; Surgery + R + AAVV: stereotactic surgery, recovery, expression of AAV vector; OF: session in test chamber with patch cord attached to optic fibre; CSS/CON: CSS protocol or control handling; SIG♀: fibre photometry signal test with proximal exposure to female; ♀D: distal sociosexual motivation test; ♀P: proximal sociosexual motivation test; BP: brains were perfused-fixed for histology. B Schematic of distal sociosexual motivation test with fibre photometric recording. Nosepoke responses at an operant stimulus triggered door opening on a fixed ratio (FR) schedule (1 trial at FR 3, 4 trials at FR 5); attaining the FR resulted in immediate opening of a sliding door, so that the mouse could access the tunnel to the stimulus compartment. A (pro-)estrous female was placed under a pencil cup through which the male could interact with the female; the stimulus phase of each trial was 1 min. Mice received two daily tests (days 1 and 2). C Distal SOM test operant phase duration i.e. time from 1st until 3rd/5th operant response. Group x Day interaction effect: F(1, 842) = 8.49, p = 0.004). D Post-operant phase z-scored DA activity from 3 s prior to until 5 s after the mouse first entered the tunnel to the stimulus compartment, for day 1 and trial 1 (left) and day 1 and trial 5 (right). Group x Time interaction effect: F(3, 1340) = 3.15, p < 0.02. E Schematic of proximal sociosexual motivation test with fibre photometric recording. Nosepoke responses at an operant stimulus triggered door opening on a fixed ratio (FR) schedule (2 trials at FR 10); attaining the FR resulted in immediate opening of a sliding door, so that the mouse could access the tunnel to the stimulus compartment. A (pro-)estrous female was placed in the social compartment and the male and female could interact; this stimulus phase of each trail was 3 min. Mice received two daily tests (days 3 and 4). F Representative traces from a CON mouse (left) and a CSS mouse (right) of z-scored NAc DA activity during FR 10 trials. For each trial, z-scores were calculated using the trial-specific baseline. G Proximal SOM test operant phase duration i.e. time from 1st until 10th operant response. Group main effect: F(1, 28) = 4.56, p < 0.05. H Post-operant phase z-scored DA activity from 3 s prior to until 5 s after the mouse first entered the tunnel to the stimulus compartment, for day 3 and trial 1 (left) and day 3 and trial 2 (right). I Proximal SOM test percent of social phase spent in social episodes. Day main effect: F(1, 84) = 14.54, p < 0.001. J Social phase z-scored DA activity from 3 s prior to until 5 s after the onset of a social episode, for day 3, trial 1 and social episode 1 (left) and day 3, trial 1 and social episode 5 (right). Group x Social episode interaction effect: F(4, 2814) = 6.87, p < 0.001; CSS > CON in social episode 1: p < 0.001, Sidak’s multiple comparisons test. In (C, G and I), statistical analysis was conducted using a linear mixed model with fixed effects of group and day and random effect of subject. In (D and H), statistical analysis was conducted using a linear mixed model with fixed effects of group, day, trial and time and random effect of subject. In (J), statistical analysis was conducted using a linear mixed model with fixed effects of group, day, trial, social episode and time and random effect of subject. Post hoc comparisons were conducted using Sidak’s multiple comparisons test. Images (B) and (E) were created with BioRender.com.