6 research outputs found
Cerebrospinal fluid sodium rhythms
Background: Cerebrospinal fluid (CSF) sodium levels have been reported to rise during episodic migraine. Since
migraine frequently starts in early morning or late afternoon, we hypothesized that natural sodium chronobiology
may predispose susceptible persons when extracellular CSF sodium increases. Since no mammalian brain sodium
rhythms are known, we designed a study of healthy humans to test if cation rhythms exist in CSF.
Methods: Lumbar CSF was collected every ten minutes at 0.1 mL/min for 24 h from six healthy participants. CSF
sodium and potassium concentrations were measured by ion chromatography, total protein by fluorescent
spectrometry, and osmolarity by freezing point depression. We analyzed cation and protein distributions over the
24 h period and spectral and permutation tests to identify significant rhythms. We applied the False Discovery Rate
method to adjust significance levels for multiple tests and Spearman correlations to compare sodium fluctuations
with potassium, protein, and osmolarity.
Results: The distribution of sodium varied much more than potassium, and there were statistically significant
rhythms at 12 and 1.65 h periods. Curve fitting to the average time course of the mean sodium of all six subjects
revealed the lowest sodium levels at 03.20 h and highest at 08.00 h, a second nadir at 09.50 h and a second peak
at 18.10 h. Sodium levels were not correlated with potassium or protein concentration, or with osmolarity.
Conclusion: These CSF rhythms are the first reports of sodium chronobiology in the human nervous system. The
results are consistent with our hypothesis that rising levels of extracellular sodium may contribute to the timing of
migraine onset. The physiological importance of sodium in the nervous system suggests that these rhythms may
have additional repercussions on ultradian functions