NA;The neuropeptides vasopressin, adrenocorticotropin lpar;ACTHrpar;, and bgr;hyphen;endorphin seem to have important effects on memory and learning. Animal studies attempting to demonstrate these effects are difficult to interpret because of the complexity of behavior that is described as ldquo;learningrdquo; and the impossibility of assessing verbal learning in animals. This article therefore reviews some of the animal literature on neuropeptides and learning, but focuses primarily upon studies in humans, both in normal volunteers and in patients with neurological disorders. Vasopressin enhances learning under some conditions. Intranasal administration has been associated with improvement on psychometric tests in patients with mild Alzheimer's disease and Korsakoff's psychosis, although these findings are not uniform. It improves performance on memory tests in normal volunteers, but does not seem to improve the memory deficit after head trauma. Cerebrospinal fluid levels are low in patients with Alzheimer's disease. ACTH and melanocytehyphen;stimulating hormone lpar;MSHrpar; are two peptides the primary behavioral effect of which seems to be on attention or goalhyphen;motivated behavior rather than on memory processes themselves. Visual discrimination and the ability to continue repetitive tasks are enhancedsemi; in mentally retarded subjects, the administration of ACTH or MSH improves performance on a variety of neuropsychological tests. It does not, however, improve cognitive function in the elderly. Endogenous opioids including bgr;hyphen;endorphin and methyphen;enkephalin seem to have primarily an amnesic effect in animal studies. Their role in human learning is still uncertain, although naloxone, which antagonizes their effects, has been associated with improved cognitive performance in patients with Alzheimer's disease. These data underscore the complexity of the processes associated with human memory and the rudimentary state of our present knowledge. Whatever the mechanisms, however, vasopressin, ACTH, and endogenous opioids seem to have important effects upon memory. lpar;Neurosurgery17colon;355hyphen;369, 1985rpar;
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