Circadian rhythms of folate and vitamin B 12 concentration in relation to convulsive thresholds of mice

Abstract

Circadian rhythms of folate and vitamin B 12 concentrations in the liver, brain and blood of Swiss mice have been determined. The relation of the changes in vitamin concentration to circadian rhythms in locomotor activity, drinking activity and convulsive thresholds (maximal electroshock seizure threshold) have been determined also. Both free folic acid (FFA) and total folic acid (TFA) of liver and blood showed minimum values at 21.00–24.00 h and maximum values at 06.00–09.00 h. Liver TFA declined at a steady rate from the peak value at 09.00 h whereas liver FFA and plasma folate maintained constant values from 09.00–18.00 h then declined rapidly. Brain folate (TFA and FFA) showed no rhythm. The concentrations of vitamin B 12 in plasma, liver and brain showed only minor fluctuations. Locomotor and drinking activities showed very similar rhythms with a sustained period of high activity between 12.00–21.00 h followed by a much shorter second period of high activity (23.00–03.00 h). Convulsive threshold declined during the first period of increased locomotor and drinking activities reaching a minimum value at 21.00 h thus just preceding the nadir in folate concentrations in liver and blood.