The effect of intrahippocampal microinjection of Naloxone on short - term and long-term memory in adult male rats

The hippocampus is one for the major centers of learning and memory. Role of the opioid system has been investigated and on the other hand receptors related to this system such as mu-opioid receptors (MOR) are extended in the hippocampus. In this study the effect of Naloxone administration as a mu opioid receptor antagonist on passive avoidance memory in adult male rats was investigated by using shuttle box instrument. In this study 45 male adult Wistar rats at range of 200± 20 were used. They were cannulated after anesthesia and Naloxone 0.5, 1, 1.5 and 2 µg/rat has been injected intrahippocampally after recovery and post training by shuttle box. Then after 90 minute short –term memory and after 24 hours long- term memory were measured posttrainingly. results showed that naloxone0.5, 1, 1.5 and 2µg/rat didn’t affected short – term memory on the other hand according to results of long-term memory showed that Naloxone 0.5 µg/rat didn’t affected memory and Naloxone 1 and 1.5 µg/rat improved memory and Naloxone 2 µg/rat impaired memory. Considering to obtained results it seems that Naloxone affected learning and memory in a dose dependent manner.