Role of Brain Β-endorphin in Memory Modulation Revisited

A possible role for the brain β-endorphin system in memory modulation was proposed by Ivan Izquierdo more than 30 years ago. Along with pharmacologic evidence of the effects of morphine and naloxone administered immediately after training in avoidance tasks and with the demonstration of medial-basal hypothalamus β-endorphin release after novelty detection, it was hypothesized that an endogenous opioid state present in the labile period of consolidation will be part of the memory of the newly acquired information. The fact that pre-test novelty exposure, through release of β-endorphin, or the injection of opioids facilitate retrieval supports that. The mechanisms through which novelty exerts its retrieval-enhancing effect were studied; evidence that several forms of amnesia induced by post-training treatments are due to unavailability of retrieval and not to a storage deficit, challenging the memory consolidation framework is discussed. In this review some of the original papers in the subject are revisited. Recent studies on the memory beneficial effects of novelty, both in animal models and in humans, indicate this is line of investigation is worth of pursuing and demonstrate the importance of the seminal work of Ivan Izquierdo in the field of memory modulation.