EFFECT OF HIGH PLASMA CHOLINE ON BRAIN AREA ACETYLCHOLINE CONTENT - DRUG INTERVENTION

The steady-state concentration (SSC) of plasma choline in rats was rapidly increased 15- and 30-fold by a technique employing two consecutive constant infusion rates of choline. Increasing the plasma SSC of choline 15-fold (to 210 nmol/ml) produced essentially no changes in brain area acetylcholine (ACh) and choline contents, except for a small increase in hippocampal ACh, while at the plasma SSC of around 450 nmole/ml, the choline content was unchanged in the striatum but increased by 20-30% in the brainstem, hippocampus and telencephalon. The ACh content was increased in the hemispheres (17%), hippocampus (21%) and striatum (34%). The i.p. administration of choline, 1299 μmol/kg, increased striatal ACh and choline contents while the i.v. administration of cytidine diphosphate choline, 943 μmol/kg, increased only striatal choline. The positive action of choline on striatal ACh, when infused or administered i.p., was blocked by atropine, and, after i.p. injection, by reserpine as well but not by methylatropine. None of these drugs prevented the increase in striatal choline. The data suggest that exogenous choline may function as a central direct muscarinic receptor agonist rather than as a precursor of ACh when it increased striatal ACh content. © 1979 The Italian Pharmacological Society.