INVOLVEMENT OF AMINO-ACIDS, OPIOIDS, NITRIC-OXIDE, AND NMDA RECEPTORSIN LEARNING AND MEMORY CONSOLIDATION IN CRICKETS

The effect of injections of selected amino acids and of N-methyl-D-asp artate (NMDA); morphine; and NMDA, nitric oxide (NO), and opioid inhib itors given before a maze-learning was investigated. Thirsty crickets (Pteronemobius sp) were trained to turn only to one side of a symmetri cal Y-shaped maze using reinforcements with water. The insects retaine d the learned task 24 h later. Nz anoxia applied immediately after tra ining produced retrograde amnesia. Injections of alanine (Ala), argini ne (Arg), glutamine (Gin), morphine, or NMDA prior to training blocked the amnesic action of anoxia. Naloxone, an opioid antagonist, blocked long-term memory formation, but not learning, whereas hemoglobin or 2 -amino-5-phosphonovaleric acid (APV), NO and NMDA antagonists respecti vely, blocked both. The antiamnesic effect of Morphine and Arg, but no t that of Ala or NMDA was blocked by naloxone. The results suggest inv olvement of NMDA receptors and NO and thus of long-term potentiation p henomena in learning and in memory consolidation, whereas other neurom odulatory systems related to Arg, and opiate receptors, are only invol ved in memory consolidation.