Opiate antagonists, morphine and spatial memory in rats

To assess the possible role of endogenous opioids on spatial memory, rats were administered morphine (1-15 mg/kg), naloxone (1-10 mg/kg), or naltrexone (0.1-10 mg/kg) at varying times after or prior to completing the first 4 choices in an 8 arm radial maze. None of these agents consistently affected retention, suggesting that endogenous opioid systems do not play a major role in modulating neural mechanisms that maintain accurate spatial memory.