Naloxone and β-endorphin alter the effects of post-training epinephrine on memory

✍ Scribed by I. B. Introini-Collison; J. L. McGaugh

• Publisher: Springer
• Year: 1987
• Tongue: English
• Weight: 825 KB
• Volume: 92
• Category: Article
• ISSN: 0033-3158
• DOI: 10.1007/bf00177921

✦ Synopsis

These experiments examined the involvement of opioid peptides in the memory-modulating effects of posttraining epinephrine (Epi). Mice were trained on inhibitory avoidance (IA) and Y-maze discrimination (YMD) tasks and given post-training injections followed by retention tests 24 h later. In the IA task retention was enhanced by low doses of Epi and impaired by high doses. In both tasks, naloxone facilitated retention and blocked the memory-impairing effects of Epi. These findings are consistent with other evidence suggesting that the memory-impairing effects of fl-endorphin are mediated by the release of opioid peptides. Previous studies have shown that a novel exploratory experience given 1 h prior to training blocks the release of brain fl-endorphin and blocks the memory-enhancing effects of post-training naloxone. In the present study we found that a novel experience given 1 h prior to training blocked the memory-impairing effect of post-training Epi otherwise obtained in both tasks. The effects of a low, memory-enhancing dose of Epi appear not to involve the release of opioid peptides: a low dose of Epi blocked the memoryimpairing effect of fl-endorphin. Further, low doses of Epi and naloxone, which were ineffective when administered alone, significantly enhanced retention when administered together. We interpret these findings as indicating that the memory-enhancing and memory-impairing effects of Epi are mediated by different mechanisms.