Pulsatile growth hormone release in the rat: failure to demonstrate a correlation with sleep phases.

Concurrent 5-hour profiles of growth hormone (GH) secretion and sleep phases were obtained in 7 rats chronically implanted with right atrial cannulae, and electroencephalographic electromyographic, and electroculographic electrodes. Hormone profiles confirmed pulsatile secretion of GH. Secretory GH episodes occurred every 3 to 4 hours and peaks generally exceeded 100 ng/ml, and, in 14 of the 21 troughs recorded, GH was unmeasurable (less than 1 ng/ml). The comparison of hormone profiles and concurrent sleep patterns excluded a temporal relationship between episodic GH secretion and sleep cycles, while scattergrams of hormone values plotted against preceding sleep phase durations also failed to demonstrate a relationship.