Increased elevated plus maze open-arm time in mice during spontaneous morphine withdrawal

Rats undergoing both naloxone-precipitated and spontaneous opioid withdrawal exhibit anxiogenic behaviors in the elevated plus maze (EPM). Recently, we observed an unexpected result, namely mice exhibited increased EPM open-arm time during naloxone-precipitated morphine withdrawal. This was surprising since this behavioral outcome is usually associated with an anxiolytic profile. This study demonstrates that mice exhibit an increase in both EPM open-arm time and % open-arm entries also during spontaneous opioid withdrawal.