Effect of social instability stress in adolescence or adulthood on sensitivity to sucrose concentration in a social context in male and female Long-Evans rats

Although there is evidence of sex differences in responding to social stress, and that age when stressed matters, females are understudied and adult-stress comparisons are few. Here, we investigated stress effects on reward sensitivity by examining rats' choice of social versus sucrose reward in a continuous spatial allocation design. We predicted social instability stress (SS) in adolescence would result in greater social discounting (spend less time near a novel peer when provided access to sucrose) relative to nonstressed controls (CTLs) and relative to SS in adulthood. All increased sucrose intake as the concentration increased, with no evidence of social discounting. SS males tested soon after the stress had a decrease in intake, whereas those tested long after had an increase in both time near the peer and in intake. CTL and SS females did not differ in intake, although their dose-response curves differed when tested soon after the SS. We also tested whether SS changed the stimulus value of the rat as a social peer; when tested in triads, CTL rats spent similar time in interaction with SS versus CTL rats. In sum, effects of SS on reward sensitivity were greater for males irrespective of administered in adolescence versus adulthood.