Long-term effects on biotransformation of labelled choline in different parts of the rat brain induced by single choline injections.

The long-term effects of single choline (Ch) injections on the uptake and metabolism of a tracer dose of 3H-Ch were studied in male rats. Choline was administered as a threshold infusion to obtain convulsions 10 and 4 weeks before sacrifice (group 1). At a single threshold infusion of choline 4 weeks before sacrifice no convulsions were induced in 50% of the animals in a second group (group 2--) whereas convulsions were induced in the remainder of the animals in this group (group 2+). Group 3 contained control animals. One min. after administration of a tracer dose of 3H-Ch the animals were sacrificed and examined for 3H-total activity, 3H-Ch, 3H-acetylcholine (3H-ACh) and 3H-phosphorylcholine (3H-PhCh). These activities were determined in three parts of the brain (cortex, striatum, midbrain + medulla oblongata). In the cortex a significant negative correlation between brain weight and 3H-ACh synthesis was seen in group 1. A comparison between group 2+ and group 2- indicated that induced convulsions were not critical for this effect. In the striatum there was a significant reduction in the total uptake of radioactivity in group 1 and group 2- when values were compared to the control group. Furthermore a significant positive correlation was found between the concentration of radiolabel and 3H-ACh synthesis and a negative relationship with the level of 3H-Ch. In the midbrain preparation the synthesis of 3H-ACh was reduced in group 1 where a significant negative correlation was found between the average threshold dose of choline and both 3H-ACh and 3H-PhCh synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)