Relationship between the three‐hour‐period sleep‐wakefulness cycle and growth hormone secretion in the immature rat.

Abstract

SUMMARY1. The temporal pattern of growth hormone (GH) secretion throughout a day and its correlation with the sleep-wakefulness cycle in the 29-31-day-old female rat were studied by serial blood sampling through an intracardiac cannula at 10-min intervals. Electroencephalograms (e.e.g.s) recorded continuously during blood sampling periods were scored into wakefulness and sleep, and the amount of sleep for every 10 min was plotted against the GH value as assessed by radio-immunoassay.2. By analysis of the power spectrum using the least-squares method, the time series of GH concentration was found to have a periodicity of approximately 3 0 h in any of the 6-h periods sampled, beginning at 12.00, 18.00, 00.00 and 06.00 h, and in either sex.3. The peak time which was estimated for the time series of GH concentrations was found to occur consistently around 02.00-03.00, 05.00-06.00, 08.00-09.00, 11.00-12.00, 14.00-15.00, 17.00-18.00, 20.00-21.00 and 23.00-24.00 h in either the male or the female rat.4. The cross-correlation analysis performed between the time series of the amount of sleep and the GH concentration, which were obtained for the 6-h period from 12.00 to 18.00 h, revealed a significant positive correlation between the GH level and the amount of sleep during the preceding 10 min.5. The time series of the amount of sleep over a 24-h period from the data obtained in the continuous recording of e.e.g.s from 27 to 31 days of age revealed an ultradian rhythm with a periodicity of approximately 3 0 h.6. These findings indicate that the rat GH secretary rhythm with a 3-0-h periodicity develops by 30 days of age in both sexes, relating to the 3-0-h-period ultradian rhythm of the sleep-wakefulness cycle entrained by the light cycle.

Effects of Gamma-Aminobutyric Acid-A Receptor Antagonist Bicuculline, on the Electrical Activity of Luteinizing Hormone-Releasing Hormone Pulse Generator in the Ovariectomized Rat

“…It has been confirmed in the immature rat that a 20% decrease in hemato crit did not cause singificant effects on the health or on the weight gain afterwards [ 19]. Further, this loss of blood was not to be stress ful for the rat on the basis of effects on growth hormone secretion which has been shown to be responsive to stress [20], Following a control period, during which at least 4 MUA volleys were recorded, muscimol (2 mg/kg. Sigma Chemical Co., St. Louis, Mo., USA) or bicuculline (2 mg/kg, (-)bicuculline methiodide.…”

Corticosterone and Growth Hormone Secretions during Long-Term Thiopental Anesthesia in the Male Rat

“…That is, (1) although the episodic secretion of GH is correlated with the sleep cycle [8,9], a decrease in the amount of sleep by a sleep-deprivation procedure induces only an attenua tion of GH secretion that occurs at the anticipated time in the 3-hour rhythm [10]; (2) there is a small number of ani mals in which a temporal dissociation of the three ultradian rhythms, i.e., GH, CS and sleep, is apparent [11], and (3) under the conditions of a continuous-sleep state induced by long-term thiopental anesthesia, the ultradian rhythms of GH are still maintained with almost the same periodicities as in the freely moving animals [13]. Thus, it was considered that each of the GH, CS and sleep rhythms was controlled by a separate pacemaker, although sharing the same basic rhythmicities.…”

“…The results demonstrate that CS and GH secretions are able to manifest the same ultradian rhythms as those in the unanesthetized, freely moving condition even in the continuous-sleep state due to thiopental anesthesia. Combined with our previous findings, the CS, GH and sleep-wakefulness rhythms appear to be governed by separate pacemakers, although sharing the same basic ultradian rhythm.Recent experiments in our laboratory demonstrated that episodic secretion of growth hormone (GH), occurring with a 3-hour periodicity, is correlated with the 3-hour period sleep cycle in the immature and adult rat [8][9][10]. It is docu mented further that secretion of corticosterone (CS) is also episodic [2,7,15] and synchronized with locomotor activity [7,15].…”

Behavioural rhythmicity in transgenic growth hormone mice: trade-offs, energetics, and sleep–wake cycles

“…Rats and mice show ultradian rhythms of sleep coupled with GH secretion over periods of 2-4 h (Kawakami et al 1984;Kimura and Tsai 1984;Mitsugi and Kimura 1985;Tannenbaum 1987;MacLeod et al 1991). GH secretion follows sleep with a lag of about 10 min (Kawakami et al 1984).…”

“…GH secretion follows sleep with a lag of about 10 min (Kawakami et al 1984). There is also circadian rhythmicity, so that most sleep occurs during the photophase (Mitler et al 1977).…”