[Development of memory-improving drugs].

Knowledge on the diverse processes involved in memory has been gained from multiple approaches, all necessary for the development of molecules aimed at enhancing memory. However, the neurobiological aspects of apprenticeship and memory remain to be fully elucidated. Long-term storage of information in the nervous system is under the control of glycoprotein synthesis. The chemistry of storage has been extensively studied in mollusks because of their simple neuroarchitecture. In mammals, the phenomenon of hippocampic long-term potentialization (HLTP), to a large extent linked to modification of glutamatergic transmissions, has been demonstrated. Stimulation of N-methyl-DL-aspartase (NMDA) receptors induces an influx of calcium, which is needed for HLTP maintenance, as are the activation of protein kinase C (PKC) and the synthesis of new proteins, for example calmodulin. At the molecular level, a cascade of biochemical events leads to modifications of neuronal connections, thus constituting the basis of memory. Memory-improving substances can be classified according to their theoretical mechanism of action: molecular pharmacology (agents inducing phenomena that mimic HLTP), neurotransmission (molecules acting on the cholinergic, noradrenergic, serotoninergic, GABAergic or dopaminergic systems), pathophysiology (substances antagonizing or correcting anomalies responsible for the memory deficiency, i.e., the cognitive enhancers). The development of memory-enhancing drugs has encountered many obstacles, notably the difficulty in evaluating the effectiveness of a medication in improving memory. It is imperative that guidelines be established for the clinical and experimental development of such substances as well as the standardization of tests in animals and man.