Effects of experimental diabetes on the concentration of corticosterone in central nervous system, serum and adrenal glands

Abstract

Experiments were conducted in male rats to study effects of streptozotocin diabetes on (a) circadian rhythms of corticosterone in hypothalamus (HT), hippocampus (HC), cerebral cortex, serum and adrenals; (b) subcellular distribution of corticosterone in HT and HC, and (c) feeding patterns. Animals were kept under controlled lighting (07–1900 h) and killed at 4 h intervals. A daily rhythm of corticosterone concentration was found in brain regions, serum and adrenals of control animals with peak levels at 2100h and minima at 1300h. In diabetics a loss of the normal circadian variation was observed, with midday increments of corticosterone concentration in serum and tissues with respect to controls. The subcellular distribution of brain corticosterone was different in diabetics, with the majority of the steroid being present in cytosol of HT and HC. Consequently the nuclear-cytosol ratio for corticosterone was markedly reduced in HT and HC of diabetic animals. The feeding pattern of diabetic rats was also changed: whereas control animals consumed most of their food and water during the dark period, intake of diabetic rats was significantly greater during the light and lower than normal during the Clark period. These results indicate a disturbance in corticosterone variation of diabetic animals, and in view that feeding schedules may synchronize adrenocortical activity, the possibility exists that the altered feeding pattern was responsible for the abnormal rhythm. The change in the nuclear to cytosol distribution of corticosterone in diabetics suggests an impairment of the biological activity of the cortieoid in brain.