AJP - Regulatory, Integrative and Comparative Physiology, Vol 239, Issue 1 35-R41, Copyright © 1980 by American Physiological Society
Circadian periodicity of brain activity and urinary excretion in the epileptic baboon
C. L. Ehlers and E. K. Killam
A 24-H rhythm in the proclivity of the baboon Papio papio to exhibit a
seizure response to intermittent light stimulation (ILS) has been
uncovered. Seizure response to ILS was found to be greatest in the morning
at about 0900 h, 2 h after lights on, and least severe in the evening at
about 2000 h 1 h after lights off. Urine cortisol and potassium excretion
rhythms followed the same pattern as seizure susceptibility and sodium
rhythms were 3 or 4 delayed. Mean values for urine cortisol per 4 h ranged
from 25 microgram/4 h at the maxima (0400 to 0800 h) to 2 microgram/4 h at
the minima (2000 to 2400 h). Electrolyte rhythms ranged from 13 to 3 meq/4
h for potassium and 1 to 5 meq/4 h for sodium. Changes in
electroencephalographic (EEG) activity also accompanied the change in urine
cortisol and potassium, and seizure sensitivity, Changes in the EEG at the
diurnal minima (2000 h) consisted of a decrease in slow waves concomitant
with an increase in fast activity in the 18-25 Hz range,
