Ultradian glucocorticoid rhythms in monkeys and rats continue during stress

Abstract

Previously we showed that rhesus monkeys have ultradian cortisol rhythms with periods of about 90 min that persist during the infusion of large amounts of adrenocorticotropin. The experiments reported here showed that rats exhibit ultradian corticosterone rhythms with a similar period (median period 61 min). However, rat ultradian corticosterone rhythms were distorted by large slow trends that had to be removed before the rhythm could be adequately assessed. The need for sophisticated trend removal suggests that physiological variables that have been described as exhibiting episodic fluctuations (e.g., human cortisol) may actually be periodic and ultradian. The ultradian glucocorticoid rhythm persisted during stress both in monkeys (median period 80 min) and rats (median period 52 min). However, the glucocorticoid stress response appeared to produce large slow trends in both monkeys and rats, indicating that environmental influences may introduce slow trends that make raw data difficult to evaluate. More importantly, the fact that ultradian glucocorticoid rhythms persist during stress provides further evidence of limits on the classical concept that glucocorticoid secretion is tightly and inseparably linked to hormonal events in the hypothalamic-pituitary unit.

Corticosterone Levels in the Brain Show a Distinct Ultradian Rhythm but a Delayed Response to Forced Swim Stress

“…Importantly, adrenal corticosterone secretion is not continuous but follows a pulsatile pattern with a periodicity of about 60 min (9). This pulsatile secretion pattern is reflected in the blood as an ultradian rhythm with a similar pulse frequency and has been reported in numerous species including rat (9 -11), sheep (12), rhesus monkey (13), and man (14,15). The increase in plasma glucocorticoid concentrations in response to stress is superimposed on the circadian secretory pattern.…”

Splanchnic Neural Activity Modulates Ultradian and Circadian Rhythms in Adrenocortical Secretion in Awake Rats

“…Since ultradian rhythms in plasma corticosteroid are maintained during exposure to stress in monkeys and in rats [22], the former possibility may hold. Alternatively, there is evidence from clinical studies that surgery shifts the diurnal rhythm of plasma cortisol in proportion to the magnitude of the surgical trauma [23].…”

Unraveling the Time Domains of Corticosteroid Hormone Influences on Brain Activity: Rapid, Slow, and Chronic Modes

“…These pulsatile patterns are maintained across the blood-brain-barrier and persist in corticosteroid target regions such as the hippocampus (Droste et al, 2008). Ultradian corticosteroid pulsatility has been described in many species (Weitzman et al, 1971;Tapp et al, 1984;Jasper and Engeland, 1991;Windle et al, 1998b;Cook, 2001). Recent studies demonstrated that corticosterone pulsatility significantly contributes to physiology by maintaining normal GR signaling and HPA axis responsiveness to stress Sarabdjitsingh et al, 2010a).…”