(A and B) OT antagonist administration reduced plasma OT concentration in all OT ANT groups, except for standard OT ANT males (n = 10–13/group). Social control females displayed higher concentration of plasma OT than any other group. No difference was found between social control females and males. (C and D) OT antagonist L-366,509 reduced telomere length in social females. Asterisks indicate significant differences: *p ≤ 0.05; **p ≤ 0.01; one-way ANOVA. Filled circles: mean OT concentrations in individual rats. Horizontal bars: mean OT concentrations in each group. ANT: antagonist, bp: basepair, OT: oxytocin, pM: picoMolar, Tel: telomere.