Effects of chronic manipulations of dietary choline on dynamic behavioural situations

Action of chronic choline administration on behavior and on cholinergic and noradrenergic systems

Chronic administration of low doses (0.2-0.8 g/kg/day) of choline caused in the rat an increase of errors evaluated in the staircase maze after 20 days of interruption of daily training. An analogous pharmacological treatment caused no modification of the acetylcholine (ACh) and norepinephrine (NE) levels and no consistent modification of the density of muscarinic and alpha 1-adrenergic receptors. Only at higher doses (2.5 g/kg/day) did chronic administration (20 days) of choline cause in several sections of the CNS, an increase of ACh and NE levels and of the muscarinic receptor density. These observations indicate that only at high doses of choline are there consistent modifications of the central cholinergic systems, suggesting that the behavioral modifications observed at low doses of choline are not determined by an upregulation of the central cholinergic system.

Dietary choline manipulations and behavioural modifications in rats in the early stages of aging

1. Behavioural effects of chronic manipulations of dietary choline in rats in the early stages of aging are reported. Rats were maintained on choline-deficient, low-choline and high-choline enriched diets. Two schedules of operant conditioning, representing "learning'h situations, plus an open field session were studied. 2. In the "temporal discrimination" test, the low-choline enriched group performed significantly better than controls while the deficient-choline group worse. The high-choline enriched group performed better than controls only in the second part of the test (where there was a stabilisation in behaviour). 3. In the "extinction" trials the high-choline enriched group retarded, while deficient-choline accelerated the extinction. In the open field sessions only the deficient-choline group, for the number of squares crossed, significantly differed from controls. 4. These observations lead us to suggest a general depressive effect in the rats on a choline-deficient diet, whereas with dietary choline supplements the effects on "learning" situations can be variable depending, on a large measure, on the test chosen.

Behavioural effects of chronic manipulations of dietary choline in senescent rats

1. Senescent rats were maintained on choline-deficient and choline-enriched diets. The modifications in rat behaviour caused by the chronic manipulations of dietary choline were studied in two schedules of operant conditioning. 2. In the "periodic conditioning" test, the schedule of reinforcement, in a 100 min trial, was changed from a fixed ratio to a fixed interval schedule. In the "reversal" test the contingency for food delivery was switched four times from one lever to the other in a two lever Skinner box. 3. In the "periodic conditioning" test, the choline enriched group (430 mg/Kg/day) showed the same reduction of responses/reinforcement as controls, from the beginning to the end of trial; in the same group the time course reduction of responses/reinforcement became significant earlier than in the control group. The deficient-choline group in the last 40 min of "periodic conditioning" trial gave a reduction of responses/reinforcement greater than controls and one rat in the group did not learn the change of experimental schedule and extinguished its operant behaviour. 4. In the "reversal" test, the choline-enriched diet (320 mg/Kg/day) improved the reinforced responses in the IV reversal; one rat of the deficient-choline group could not learn the new operant schedule since the first reversal and continued to respond on the same lever during the whole of the test.