Brain methionine- and leucine-enkephalin receptors in patients with dementia

Brain [ 3H]Met- and [ 3H]Leu-enkephalin binding was studied in patients with Alzheimer's disease (AD) and vascular dementia (VD), and in age-matched controls. Brain areas investigated were the internal and external globus pallidus, amygdala, hippocampus and temporal cortex. In AD, the binding of both enkephalins decreased in all brain areas examined, except in the external globus pallidus for both enkephalins and in the internal globus pallidus for leucine-enkephalin. Scatchard analysis of amygdaloid samples showed a decrease in the number of receptors (Bmax) without any change in their affinity ( K d). In patients with VD, no significant changes in enkephalin binding were seen. Thus, in AD, enkephalin binding (mainly reflecting delta opioid receptor subtype) is decreased, especially in limbic areas.