Transgenerational effects on anxiety-like behavior following adolescent morphine exposure in female rats

Global opioid use and misuse remains high, despite efforts to decrease rates of prescribing and diversion. Chronic exposure to opioids, particularly during critical periods of development, can lead to long-lasting effects, including effects that may extend to future generations. Using a rodent model, we have demonstrated significant transgenerational effects of female adolescent morphine exposure, despite the absence of in utero drug exposure. While these effects have been observed in both sexes, effects on anxiety-like behavior were only observed in F1 females. The current study was designed to examine both inter- and transgenerational effects of adolescent morphine exposure on anxiety-like behavior. Female Sprague Dawley rats were administered increasing doses of morphine (5-25 mg/kg s.c.) or saline for 10 days during adolescence (PND30-39). Adult diestrous female offspring (MORF1 or SALF1) and grand offspring (F2) were tested for anxiety-like behavior using the elevated plus maze (EPM). F1 females cross-fostered to donor mothers were also examined. The results show that MORF1 and MORF2 females spend significantly more time on the open arms of the EPM compared to SALF1 controls, an effect that persisted in cross-fostered females. Additional studies demonstrate that this effect is estrous cycle dependent, as decreased anxiety-like behavior was observed in diestrus, while increased anxiety-like behavior was observed in estrus. These behavioral effects were not associated with any differences in circulating corticosterone either at baseline or following EPM testing. Thus, female adolescent morphine exposure alters the regulation of anxiety-like behavior in an estrous-dependent manner and this effect persists in the F2 generation.