Figure 5. Oxytocin (OXT) decreases licking for sucrose.

Mean (± s.e.m.) licks to sucrose of 15 mice injected (i.p.) with saline or 0.1 mg/kg OXT 30-min prior to behavioral sessions. Sucrose concentrations (0, 0.03, 0.1, 0.2, 0.3, 0.6, and 1.0 M) were presented in random 5-s trials. Lick rates were standardized using the standardized lick ratio (see Methods). A, relative to saline (open symbols), licking for sucrose was significantly reduced by OXT (closed symbols). ** denotes main effect of Treatment: F(1,14) = 20.10, p = 0.00052; Treatment × Concentration interaction: F(6,84) = 8.60, p <0.0001). Post-hoc t-tests (Bonferroni correction) between OXT and saline at each concentration reveal a significant difference at 0.3 M (t(14) = 5.13, p = 0.0011). To better understand effects across the full concentration range, 3-parameter sigmoidal functions (solid lines) were fit to the concentration-response data for each animal. The lower asymptote and slope were unaffected by OXT, but the EC₅₀ was significantly shifted by 0.109 log units (t(13) = -4.290, p= 0.00088; one mouse removed for poor curve fit). B, C, male (squares) and female (circles) mice are compared for the saline session and OXT session, respectively. No differences were found.