The effect of pyritinol, a commonly used nootropic drug, on receptor properties and function was investigated in different neuronal systems, possibly associated with age-related decline in brain function. Chronic treatment (15 days) of aged (22 months) female NMRI mice with pyritinol (200 mg/kg) restored the reduced density of N-methyl-D-aspartate receptors in the aged mouse brain. Furthermore, the total number of binding sites of the alpha2-receptor ([H-3]yohimbine binding) decreased after treatment with drug, while the number of high-affinity agonist binding sites ([H-3]UK 14304 binding) was not changed. In both systems, receptor affinity was not influenced. The densities of other receptors investigated (muscarinic-cholinergic, benzodiazepine and beta-adrenergic) were not altered by treatment with pyritinol. Additionally, the effect of pyritinol on phosphatidylinositol (PI) metabolism was investigated in dissociated neurones from young and aged mice. Muscarinic-cholinergic induced accumulation of phosphatidylinositol and the inositol phosphate response due to activation of G-protein by fluoride was increased in aged animals, treated with drug. The inositolphosphate response after stimulation with pilocarpine was slightly but not significantly increased. The metabolism of phosphatidylinositol in young animals was not altered by treatment with drug. These results support the hypothesis of a nootropic-mediated restoration of age-related brain deficits. Changes caused by pyritinol may be due to beneficial effects on age-related alterations of the properties of the neuronal membrane.
