Reduction of folate levels in the rat: Difference in depletion between the central and the peripheral nervous system.

1. Rats were deprived of dietary folate for 12 and 9.5 months in two experiments; one with and one without succinylsulfathiazole added to the diet. Folate levels decreased faster in the former experiment and the final blood values were lower. Tissue folate was examined in the latter experiment only. 2. The animals were repeatedly examined with neurological tests and compared with a control group supplemented with folic acid. Every test proved normal. Measurement of motor nerve conduction velocities after 12 months in the experiment where succinylsulfathiazole was given revealed lower velocities in the non-supplemented group. There was no difference between the groups in the experiment without succinylsulfathiazole. 3. In the latter experiment brain folate was reduced by only 16% in the non-supplemented animals compared with the controls, whereas whole blood folate fell by 60%, liver folate by 50% and sciatic nerve folate by 59%. 4. The central nervous system is resistant to systemic folate depletion, whereas the peripheral nerves are depleted to the same degree as the extra-neural tissues.