Opioids and Stress: The Role of ACTH and Epinephrine. In: Taché Y, Morley JE, Brown MR, editors. Neuropeptides and Stress. New York: Springer; 1989. pp. 313-24. [DOI: 10.1007/978-1-4612-3514-9_24]

The impact of stress and discomfort on experimental outcome

Stress refers to a physiological and emotional state of man and higher animals in which the autonomic regulation is overstrained and temporarily disturbed under the impact of conflicting stimuli. Stress activates, invigorates, acts life-sustaining, and initiates and drives adaptive changes towards improved fitness. While the positive action is commonly underestimated, much attention is given to the discomfort and the strain of efforts required during coping. The label of stress as being bad and the core of suffering has been applied with particular empathy to laboratory animals, for they are kept in captivity and are exposed to experimental procedures. The husbandry conditions to which the animals are adapted are commonly standardized. This applies to procedures for subacute and chronic toxicity testing. Acute toxicity tests are the classical example of stress research in which the demands on the organism exceed the limits of its regulative capacity. Stressors are: the test compound, the procedure proper and preceding treatment of the animal. The experimental stress contributes to model the real situation. The weighting between the stressors may modify the outcome of the test.

Endogenous opioid peptide level changes under electrostimulation and their assessment by the EEG

Endogenous opioid peptide (EOP) system plays an important role in the interaction of human organism with different stress factors, providing stress-limiting and stress-protective functions. Different kinds of electrostimulation seem to produce anti-stress and pain relief effects due to EOP system activation. The presented paper reviews recent literature concerning EOP system activation under electrostimulation and its reflections in the EEG characteristics. The results and opportunities of high resolution EEG structure analysis utilization for EOP level control, as well as for stress-induced state assessment and correction via resonance activation of brain EEG oscillators by means of frequency-tuned external stimulation are presented.

Hydroxyurea: relationship between toxicity and centrally-induced adrenal activation

The anticancer drug hydroxyurea (HU) at doses of 300-800 mg/kg/day causes a dramatic lethality (up to 100% after a 5-day treatment) in hypophysectomized as well as in adrenalectomized rats drinking physiological saline + 5% glucose. Mortality in controls was less than 10% over a 5-day period. Adrenal stimulatory or replacement therapies protect pituitary- or adrenal-ablated rats against HU toxicity. They also counteract white blood cell changes induced by the drug. HU (30-800 mg/kg) induces a dose-dependent increase of plasma corticosterone in normal rats after single or repeated treatments that is not observed in hypophysectomized animals. HU also increases plasma levels of epinephrine, although this finding cannot account for the rise in plasma corticosterone; indeed, it is secondary to a strong rise in plasma corticosterone. The stimulation of the hypothalamic-hypophyseal-adrenal axis induced by HU is responsible for the drug-induced adrenocortical activation. This activation appears to be a valuable defence mechanism protecting intact rats against HU lethality, and its failure causes the dramatic HU lethality in pituitary- or adrenal-ablated animals.