Jürgen Guldner

Effects of Growth Hormone-Releasing Hormone and Somatostatin on Sleep EEG and Nocturnal Hormone Secretion in Male Controls

When applied centrally to animals, growth hormone-releasing hormone (GHRH) stimulates slow-wave sleep (SWS), whereas somatostatin (SRIF) increases REM sleep. We investigated whether these peptides also affect the sleep EEG in humans when given intravenously by comparing polysomnographically the effects of four boluses of (1) placebo, (2) 50 micrograms GHRH or (3) 50 micrograms SRIF administered at 22.00, 23.00, 24.00 and 1.00 h to 7 male controls. In addition, we collected blood samples through a long catheter every 20 min from 22.00 to 7.00 h and measured plasma cortisol and growth hormone (GH) levels. In comparison with SRIF and placebo, GHRH produced a significant increase in plasma GH concentration throughout the night (mean +/- SD: 10.8 +/- 2.0 ng/ml after GHRH; 3.0 +/- 1.7 ng/ml after SRIF and 3.2 +/- 2.0 ng/ml after placebo). SRIF failed to substantially attenuate the nocturnal GH release. Nocturnal cortisol secretion was blunted after GHRH but remained unaffected by SRIF (61.4 +/- 12.9 ng/ml after placebo; 46.6 +/- 19.7 ng/ml after GHRH and 70.8 +/- 12.6 ng/ml after SRIF). Quantitative sleep EEG staging showed a significant increase in SWS after GHRH administration but no change after SRIF (percent spent in SWS per night: 14.0 +/- 5.6 after placebo, 20.2 +/- 6.6 after GHRH and 15.1 +/- 8.2 after SRIF). Application of SRIF was accompanied by a trend toward increased REM density. The effects of episodic GHRH administration upon SWS, GH and cortisol secretion were opposite to those previously reported for corticotropin-releasing hormone, which supports the view that neuroregulation of human sleep involves an interaction of central GHRH and corticotropin-releasing hormone.

Neurosteroid pregnenolone induces sleep-EEG changes in man compatible with inverse agonistic GABAA-receptor modulation.

The steroid pregnenolone (P) and its sulfate (PS) can accumulate in the central nervous system independent of peripheral sources. Pharmacologically, the sulphated form of P interacts with the GABAA receptor complex, and functional assays show that this steroid behaves as an allosteric GABAA receptor antagonist. The present study explored the effect of a single dose of P upon the sleep-EEG and concurrent secretion of growth hormone and cortisol in male volunteers. P increased the amount of time spent in slow wave sleep and depressed EEG sigma power. Sleep-associated nocturnal cortisol and growth hormone secretion remained unchanged, ruling out the possibility that P exerted its effect via altered regulation of these hormones. Furthermore, results from in vitro studies on the potency of P to activate gene transcription via corticosteroid receptors made a genomic action of P via hormone receptor-sensitive DNA sequences unlikely. We conclude that P acts in a non-genomic fashion at or in the vicinity of the benzodiazepine binding site, modulating allosterically the GABAA receptor like a partial inverse.

Trimipramine and imipramine exert different effects on the sleep EEG and on nocturnal hormone secretion during treatment of major depression

In a 4-week double-blind clinical trial we compared the effects of the tricyclic antidepressants trimipramine and imipramine on the sleep EEG and on nocturnal bormone secretion in 20 male inpatients with major depression. Both treatments produced rapid significant clinical improvement in depression without severe adverse effects. However, the two drugs had markedly different neurobiologic profiles. Trimipramine enhanced rapid eye movement (REM) sleep and slow wave sleep, whereas imipramine suppressed REM sleep and showed no effect on slow wave sleep. Total sleep time and the sleep efficiency index increased under trimipramine but not under imipramine. Nocturnal cortisol secretion decreased with trimipramine but remained unchanged with imipramine. In contrast to imipramine, trimipramine induced an increase in prolactin secretion compatible with its known antagonism at dopamine (D2) receptors. Imipramine induced a decrease in growth hormone secretion during the first half of the night. Neither of the drugs induced significant changes in plasma testosterone concentration. We conclude that trimipramine is an antidepressant with sleep-improving qualities that possibly acts through inhibition of hypothalamic-pituitary-adrenocortical system activity by a yet unknown mechanism.

Reduced Efficacy of Growth Hormone-Releasing Hormone in Modulating Sleep Endocrine Activity in the Elderly

In aging, a decline in sleep continuity, a decreased slow wave sleep, an earlier nocturnal cortisol rise, and a blunted growth hormone (GH) secretion occur. Pulsatile administration of GH-releasing hormone (GHRH) in young controls enhanced slow wave sleep and suppressed cortisol release. We administered GHRH 4 x 50 microg or placebo i.v. to 13 healthy seniors (5 women, 8 men, mean age 69.3 y +/- 8.3 SD). We observed significantly reduced nocturnal awakenings and an increased first non-rapid-eye-movement sleep period. In a subgroup (n = 9), we found a significant activation of GH secretion but unchanged cortisol secretion. Our data underscore that GHRH is capable of promoting sleep in the elderly, but much less than in young subjects. Contrasting to young subjects, the hypothalamic-pituitary-adrenocortical system remains unaffected by GHRH in the elderly. These results provide further evidence that a decrease in the efficacy of GHRH is involved in the biological mechanisms underlying aging.

Changes in sleep-endocrine activity after growth hormone-releasing hormone depend on time of administration

When administered intravenously (i.v.) in a pulsatile mode during the first half of the night to young normal controls, growth hormone‐releasing hormone (GHRH) results in increased growth hormone (GH) plasma levels and slow wave sleep (SWS) and blunted cortisol release. In the present study we investigated whether GHRH has the same effects when administered in the early morning. Seven normal young male volunteers had 2 sessions each in the sleep laboratory (23.00 to 10.00 h) during which the secretion of GH, cortisol and corticotropin (ACTH) and polygraphic recordings were monitored. Verum (4 bolus injections of 50 μg GHRH) or placebo were injected i.v. at 04.00, 05.00, 06.00 and 07.00 h. GHRH stimulated GH plasma levels significantly whereas cortisol and ACTH were not altered. In the sleep‐electroencephalogram, only rapid‐eye‐movement density was decreased significantly during the period of active medication; all other sleep parameters were unaffected. We suggest that the physiological occurring high activity of the hypothalamic‐pituitary‐adrenocortical(HPA) system in the early morning prevents the effects of GHRH on cortisol plasma levels and SWS. Thus GHRH administered to healthy young men in the early morning hours has the same effect as GHRH administered during the first half of the night to patients with major depression who have HPA hyperactivity throughout the day.

Functional properties of deoxycorticosterone and spironolactone: Molecular characterization and effects on sleep-endocrine activity

Adrenal steroid hormones are capable of interfering with a variety of behavioral phenomena including sleep. The mechanisms appear to involve effects at the cell membrane as well as nuclear actions mediated by intracellular mineralo- and glucocorticosteroid receptors (MR and GR). We employed the MR agonist deoxycorticosterone (DOC) and the MR antagonist spironolactone (SP) to study the role of MRs in the regulation of human sleep. We also tested whether the effects of DOC upon the sleep EEG and nocturnal hormone secretion (growth hormone and cortisol) are compatible with those predicted for its major metabolite tetrahydro-DOC (THDOC): electrophysiological and animal experiments had suggested that THDOC would act as a hypnotic via positive modulation of the GABAA receptor. Because neither DOC nor SP affected the sleep EEG substantially, the involvement of MRs in the regulation of sleep needs further study. The sleep-endocrine data showed a suppressive effect of DOC upon plasma cortisol concentrations and an earlier occurrence of nocturnal GH maxima, which can be plausibly explained by GR or sigma receptor-mediated effects. Molecular characterization of DOC and SP confirmed a relatively strong effect of DOC upon transactivation via MR and no effect of SP on the GR-mediated transcription rate. In addition, the possibility that a low dose of the mineralocorticoid DOC may serve as a prodrug for the potential hypnotic THDOC is not supported by the current data.

Growth Hormone-Releasing Hormone (GHRH)- induced effects on sleep EEG and nocturnal secretion of growth hormone, cortisol and ACTH in patients with major depression

Studies in normal human subjects and animals suggest that the neuropeptide growth hormone-releasing hormone (GHRH) is a common regulator of the sleep EEG and nocturnal hormone secretion. In healthy volunteers GHRH prompts an increase in the amount of slow wave sleep (SWS) and in growth hormone (GH) secretion and blunting of cortisol release. Inhibition of GHRH may contribute to sleep-endocrine aberrances during depression. We tested the effects of pulsatile application of 4 x 50 micrograms GHRH on the sleep EEG and simultaneously investigated nocturnal hormone secretion in 10 inpatients (four females, six males) with the acute episode of major depression. In contrast to the effects of placebo, GH secretion increased distinctly and rapid-eye-movement (REM) density decreased during the second half of night. No other significant changes in sleep-endocrine activity, including SWS, cortisol and ACTH secretion, could be observed. We assume that hypothalamic-pituitary-adrenocortical system activity and slow wave sleep are inert to the influence of GHRH during acute depression. Cortisol and ACTH remained unchanged even in a subsample of five younger (aged 19-28 years) patients. This observation is in contrast to our recent finding that cortisol secretion is blunted in young normal volunteers after GHRH. But on the other hand, GHRH is capable of stimulating GH and inducing a decrease in REM density in these subjects.

Effects of thyrotropin-releasing hormone on the sleep EEG and nocturnal hormone secretion in male volunteers.

Various peptides including corticotropin-releasing hormone (CRH) exert selective effects on sleep structure and noctural secretions of cortisol and growth hormone (GH). In animal studies analeptic effects and sleep disturbances after thyrotropin-releasing hormone (TRH) administration have been observed; studies of endocrine function in depressed patients suggest a pathological activity of CRH and TRH as compared with that in healthy volunteers. As the role of TRH in the regulation of the sleep endocrine pattern in humans has not yet been clarified, we performed a study to examine the effects of pulsatile administration of TRH on the sleep EEG pattern and the nocturnal secretions of cortisol and GH in 7 healthy male subjects. The sleep EEG was recorded from 23.00 to 07.00 h, and blood samples were collected every 20 min from 20.00 to 07.00 h for the analysis of GH and cortisol concentrations during intravenous administration of placebo or 4 × 50 µg TRH at 22.00, 23.00, 24.00, and 01.00 h. In contrast to the well-known effects of CRH on the sleep endocrine pattern, TRH exerts only a weak effect on the sleep EEG which is reflected in a slight decrease in sleep efficiency associated with a trend to wakefulness during the night. Furthermore, after TRH administration, the cortisol rise appeared earlier, and a nonsignificant tendency to an increased secretion of cortisol during the first half of the night was found. The GH secretion did not differ significantly after application of TRH or placebo. The activating, albeit weak, effect of TRH on the sleep EEG and nocturnal cortisol secretion in healthy volunteers confirms and adds to the results previously observed in animals. On the basis of these findings, we surmise that TRH may contribute to the disturbed sleep continuity seen in depressed patients, probably acting as a cofactor of CRH in a synergistic manner.

Flumazenil exerts intrinsic activity on sleep EEG and nocturnal hormone secretion in normal controls

The physiological function of benzodiazepine (BDZ) receptors includes regulation of sleep and neuroendocrine activity. Most of the pharmacological effects of BDZ are blocked by flumazenil. However, recent neurological and behavioral studies suggest that flumazenil has its own central intrinsic activity. This issue was addressed in a study of the sleep EEG and the nocturnal secretion of growth hormone and cortisol in ten normal male controls, who were given flumazenil either alone or in combination with the BDZ agonist midazolam, placebo and midazolam alone. Flumazenil prompted an increase in sleep onset latency, a decrease in slow wave sleep and an increase in wakefulness. Plasma cortisol concentrations after flumazenil administration were lower than after midazolam. Both flumazenil and midazolam decreased nocturnal growth hormone secretion. After simultaneous application of both BDZ receptor ligands the growth hormone blunting was amplified. Our study demonstrates that at the level of the sleep EEG and neuroendocrine activity flumazenil is capable of exerting both agonistic and inverse agonistic or antagonistic effects.

Bretazenil modulates sleep EEG and nocturnal hormone secretion in normal men

Preclinical data suggest that the imidazo-diazepinone derivative bretazenil (Ro 16-6028) has anxiolytic and anticonvulsant properties with only weak sedative effects. We examined the influence of oral administration of 1 mg bretazenil on the sleep EEG and the concomitant nocturnal secretion of cortisol, growth hormone and prolactin in ten healthy young men. After bretazenil we found a significant increase in stage 2 sleep and a significant reduction in stage 3 sleep. REM latency was prolonged. Spectral analysis of sleep-EEG power revealed a decrease in delta and in theta power and an increase in sigma power. We found no significant influence on sleep onset latency or on intermittent wakefulness. Bretazenil prompted a significant decrease in cortisol secretion and a significant increase in prolactin release. It had no major influence on growth hormone secretion.