J. Josko, LIBERATION OF THYREOTROPIN, THYROXINE AND TRIIODOTHYRONINE IN THE CONTROLLABLE AND UNCONTROLLABLE STRESS AND AFTER ADMINISTRATION OF NALOXONE IN RATS, Journal of Physiology and Pharmacology, 47(2), 1996, pp. 303-310
The aim of this study was to investigate whether controllable stress,
in which the animal can avoid a stressor, and uncontrollable stress, i
n which the animal can not avoid its influence change the activity of
the endocrine pituitary-thyroid axis and whether these changes are mod
ified by naloxone - the antagonist of opioid receptors. The experiment
s were carried out on rats using electric foot shock as a stressor and
the concentration of thyreotropin, thyroxine and triiodothyronine in
the blood was determined with radioimmunoassay. The uncontrollable str
ess caused the inhibition of secretion of the hormones mentioned above
, but the controllable stress did not influence their secretion. Nalox
one administered centrally to lateral ventricle of the brain decreased
the inhibitional influence on the pituitary-thyroid axis. The obtaine
d results suggest that change of pituitary-thyroid axis activity durin
g the stress depends not only on the stressor but also on the animal's
abilities to control that stressor.