Stress responsiveness varies over the ultradian glucocorticoid cycle in a brain-region-specific manner.

Glucocorticoid hormones are released in rapid hourly hormone bursts by the adrenal gland. These ultradian oscillations are fundamental to hypothalamic-pituitary-adrenal activity and transcriptional regulation of glucocorticoid responsive genes. The physiological relevance of glucocorticoid pulsatility is however unknown.

Recovery from disrupted ultradian glucocorticoid rhythmicity reveals a dissociation between hormonal and behavioural stress responsiveness.

Ultradian release of glucocorticoids is thought to be essential for homeostasis and health. Furthermore, deviation from this pulsatile release pattern is considered to compromise resilience to stress-related disease, even after hormone levels have normalised. In the present study, we investigate how constant exposure to different concentrations of corticosterone affects diurnal and ultradian pulsatility.

Specificity of glucocorticoid receptor primary antibodies for analysis of receptor localization patterns in cultured cells and rat hippocampus.

After glucocorticoid stimulation, glucocorticoid receptors (GRs) are translocated to the nucleus to modulate transcription of glucocorticoid target genes. The subcellular distribution and trafficking of GR in cultured cells has been studied quite intensively using several techniques. However, the intracellular localization of nuclear receptors in ligand-free and stimulated conditions in vivo is still controversial, in part because of inconsistent results with different antibodies.

Disrupted corticosterone pulsatile patterns attenuate responsiveness to glucocorticoid signaling in rat brain.

Chronically elevated circulating glucocorticoid levels are although to enhance vulnerability to psychopathology. Here we hypothesized that such sustained glucocorticoid levels, disturbing corticosterone pulsatility, attenuate glucocorticoid receptor signaling and target gene responsiveness to an acute challenge in the rat brain. Rats were implanted with vehicle or 40 or 100% corticosterone pellets known to flatten ultradian and circadian rhythmicity while maintaining daily average levels or mimic pathological conditions.

Subregion-specific differences in translocation patterns of mineralocorticoid and glucocorticoid receptors in rat hippocampus.

Corticosteroids exert important effects on brain function via glucocorticoid (GRs) and mineralocorticoid receptors (MRs) by inducing receptor translocation to the nucleus, where the receptor-ligand complexes modulate transcription of target genes. Based on studies describing uneven receptor expression patterns, regionally different corticosterone effects, and the importance of timing of corticosteroid effects, we hypothesized that differential patterns of MR and GR translocation exist in the rat hippocampus in response to a single glucocorticoid stimulus. Temporal patterns of receptor translocation were investigated in both intact and adrenalectomised (ADX) male Sprague-Dawley rats.