Fig. 3.

The effects of oxytocin (OT) injected into the caudal ventral tegmental area (VTA) on social reward. a–c Males and females were injected with either 9 μM OT or saline into the VTA 5 min  prior to each of the three social interaction conditioning sessions in the conditioned place preference test. a The inverted U hypothesis predicts that injection of 9 μM OT will decrease social reward in females but increase social reward in males. b As predicted, OT injected into the VTA decreased the change in the time spent in the social interaction paired chamber compared to saline controls during the post-test in females (Social Oxytocin); but in males, OT increased the change in the time spent in the social interaction paired chamber compared to saline controls. c In females, OT injected into the VTA decreased the change in the social chamber preference score compared to saline controls (Social Oxytocin); but in males, injection of OT increased the change in the social chamber preference score compared to saline controls just missed statistical significance. d–f The effects of oxytocin (OT) (0.9 μM) injected into the VTA on social reward in males and females. d The inverted U hypothesis predicts that injection of 0.9 μM OT into the VTA will decrease social reward a small amount in females and increase social reward a small amount in males, but that the absolute amount of social reward would be similar in males and females. e In both males and females, OT injected into the VTA (Social OT) had no statistically significant effect on the change in the time spent in the social interaction paired chamber during the post-test compared to controls (Social Saline). There was, however, a trend for OT to decrease the time spent in the social interaction paired chamber in the post-test compared to controls in females and for OT to increase the time spent in the social interaction paired chamber compared to controls in males. f In females, there was a trend for OT injected into the VTA to decrease the change in the social chamber preference score compared to controls and in males, the increase in the change in the social chamber preference score compared to controls just missed significance. g–i The effects of oxytocin (OT) injected into the VTA on social reward in females given only a single social interaction conditioning session. g The inverted U hypothesis predicts that reducing the dose of social interaction would place females on the ascending slope of the inverted U-shaped relationship and, as a result, injection of 9 μM OT would increase social reward instead of decreasing it as it did when the dose of social interaction was higher. h OT injected into the VTA increased the change in the time spent in the social interaction paired chamber during the post-test compared to saline injections. i OT increased the change in the social preference score compared to saline injections. (*indicates significant difference between drug groups, *for p < 0.05, **for p < 0.01, ***for p < 0.001; + indicates significant difference between sexes, p < 0.05)