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Adrenal corticosterone (CORT) levels and ornithine decarboxylase (ODC) activities in thyroid intact, thyroidectomized, and thyroxine (2 micrograms/ml in drinking water for 3 weeks) supplemented rats were measured 11 days after adrenal sham surgery or enucleation. Thyroidectomy decreased and thyroxine supplementation increased adrenal CORT significantly (p < 0.05) at 0600 h and 1800 h. The ODC activity was not significantly affected by thyroidectomy. Thyroxine supplementation however, inhibited ODC activity significantly (p < 0.05) at 1800 h in the regenerating adrenal cortex. Results indicated that, while CORT response in normal and regenerating adrenals are positively related to thyroid manipulation, inhibition of adrenal ODC activity by thyroxine may affect adrenal regeneration.

The effects of immobilization stress and/or dexamethasone (DEX) on the adrenal ornithine decarboxylase (ODC) activities of sham-operated and adrenal-medulloectomized (enucleated) male Sprague-Dawley rats were investigated. On day 11 after surgery, rats were injected with saline or DEX (1 mg/kg), 3 h before the time of sacrifice (0600 h or 1800 h). Four groups, from sham-operated and enucleated rats (ENU) treated with saline or DEX were subjected to immobilization stress for 1 h prior to sacrifice. Groups of rats from stress-sham-DEX, non stress-sham-DEX, stress-sham, non stress-sham, stress-ENU-DEX, non stress-ENU-DEX, stress-ENU, and non stress-ENU were sacrificed at 0600 h or 1800 h on day 11 after surgery. Adrenal glands were excised and later analyzed for ODC activities. Results indicated that DEX and/or immobilization stress inhibited ODC activities (p<0.05) in normal and regenerating adrenal glands at 1800 h and ODC activity varies diurnally, the activity being greater at 1800 h than at 0600 hours (p<0.001).

Choline acetyltransferase (ChAT) activity was determined in cerebral cortex, hypothalamus, hippocampus, cerebellum, medulla oblongata, midbrain and adrenal gland of rats exposed to acute or chronic stress. The exposure of animals to acute immobilization and cold stress (4 degrees C) for one hour resulted in a significant decline of ChAT activity in all brain regions examined except for the medulla oblongata. Moreover, the exposure to acute stress resulted in significant increase of the same enzyme in the adrenal gland. However, chronic exposure of animals to cold stress (4 degrees C) for 7 days resulted in no significant changes of ChAT activity in all tissues examined except for a decline in the midbrain and an increase in the medulla oblongata. The administration of corticosterone (2.0 mg/kg) 1 h prior to sacrificing caused an effect similar to that of acute stress on ChAT activity in all brain regions except for the hypothalamus and the cerebellum. It was concluded from this experiment that stress-induced changes in the ChAT activity of specific brain regions might be mediated by the adrenal steroids.

Acetylcholinesterase (AchE, EC 3.1.1.7) activity was determined in cerebral cortex, hypothalamus, adenohypophysis and adrenal gland in response to acute and chronic stress. Chronic exposure of animals to cold stress (at 4 degrees C for 7 days) resulted in significant decline of AchE activity in all tissues studied. Similar results were obtained when animals were exposed to acute immobilization and cold stress (at 4 degrees C) simultaneously. In another experiment, animals were treated with 2 mg/kg of corticosterone prior to AchE determination. Corticosterone administration resulted in a significant decline in AchE activity of the cortex, the hypothalamus and the adrenal but failed to affect the adenohypophysis AchE level. Exposing adrenalectomized animals to acute stress resulted in no significant changes in the cortex and the hypothalamus but caused a significant decline in AchE of the adenohypophysis. It was concluded from this study that corticosterone might mediate the stress effect on AchE activity.

In this experiment, the adrenal medulla was removed from male rats and after 11 days, animals were sacrificed and the adrenal glands were incubated. Addition of epinephrine to the regenerating gland resulted in significant increase in corticosterone content in the gland. However, no significant changes were observed in the intact glands after epinephrine administration. The results of this experiment suggest that epinephrine may be playing a role in the adrenal cortex function.

The effect of a large ethanol (ETOH) dose (4.8 g/kg) on triglyceride (TG) levels of plasma, brain and liver was studied in the rat. TG levels were measured in fasted male rats treated with ETOH or after ETOH and tetraethylammonium treatment in intact rats. The levels of TG were also measured after treatment with ETOH and dexamethasone (DXM) in adrenalectomized rats. Plasma TG levels significantly increased in the nonadrenalectomized and adrenalectomized rats by one- and twofold respectively. Brain TG levels increased significantly when intact animals were placed under either stress or when they were treated with ETOH and stress simultaneously. The adrenalectomized rats showed a similar response when they were treated with ETOH and DXM simultaneously. The liver TG levels were significantly different from control in all treated animals. The ETOH-treated adrenalectomized rats' TG levels were significantly less than control. This study suggests that stress and the adrenal gland play important roles in ETOH-induced TG levels in the rat.