E-ISSN : 2733-4538
The present experiment was conducted to determine whether the paradoxical hypoalgesia induced by naloxone-heat pairings is due to fear elicited by naloxone pretreatment and the latencies with paw-lick, rearing, and jump were recored as an index of response to the pain. In the result of experiments, the rats pretreated with naloxone were tended to shorter latenceis than saline control rats in jump but, they did significantly different in the paw-lick response. However, naloxone pretreated groups were not different in the paw-lick latencies according to drug dosage. In the test of anxiolytic drug, diazepam did not influnced rearing and jump but, significantly reduced paw-lick latency in the rats trained with naloxone-heat pairings. These results were suggested that fear is important factor in the paradoxical hypoalgesia elicited by naloxone-heat pairings.