phosphorus-radioisotopes and naltrindole

In striatal membrane preparation used for receptor binding experiments high levels of protein phosphatase 1 and 2A activities were detected using [32P]phosphorylase a as substrate. Sodium chloride decreased the activity of protein phosphatase 2A and increased the activity of protein phosphatase 1 in a concentration-dependent manner. Sodium chloride facilitated the saturation binding of naloxone and naltrindole in rat striatal membrane preparation preincubated with ATP (50 microM) and MgCl2 (5 mM). Preincubation with calyculin A (1 nM) further increased the binding of naloxone. Addition of okadaic acid in a concentration of 2 nM, which is specific for the inhibition of protein phosphatase 2A, augmented the number of binding sites of naloxone or naltrindole. The results suggest a protein phosphatase-dependent regulation of the binding of opiate ligands in the striatum.

Topics: Animals; Corpus Striatum; Enzyme Activation; Enzyme Inhibitors; Male; Marine Toxins; Naloxone; Naltrexone; Narcotic Antagonists; Oxazoles; Phosphoprotein Phosphatases; Phosphorus Radioisotopes; Phosphorylase a; Protein Phosphatase 1; Protein Phosphatase 2; Rats; Rats, Wistar; Receptors, Opioid; Sensitivity and Specificity; Sodium Chloride; Substrate Specificity; Tritium