title: Adaptation of the adrenocortical response during repeated stress in thalamic pigeons.
abstract: Chronic vascular catheterization allowed to obtain serial blood samples before and after stress application to thalamic pigeons. Daily repetition of the same stress, at the same hour, for 5 weeks led to drastic changes in the stress-induced adrenocortical reaction. The rebounding, long-lasting rise in plasma corticosterone occurring after initial presentation of electrical footshocks was replaced by a single peak of corticosterone, lower and shorter than the initial response. Moreover, an anticipatory conditioned rise in corticosterone appeared before stress. Random distribution of stressful stimuli, thrice a day, for 5 weeks resulted in the single peak pattern of post-stress adrenocortical reaction, without any anticipatory component. When electrical footshocks were omitted after 5 weeks of daily regular presentation of stress, only the anticipatory peak in plasma corticosterone occurred. Shifting the daily lighting from the usual 06.00 a.m. to 04.00 a.m. led to a shift in the anticipatory conditioned endocrine response which appeared 2 h sooner than usual. Thalamic involvement in the process of adaptation to chronic stress is discussed.
mesh_terms: D000222:Adaptation, Physiological; D000302:Adrenal Cortex / Q000503:physiopathology*; D000818:Animals; D010856:Columbidae; D003213:Conditioning, Psychological / Q000502:physiology; D005260:Female; D008297:Male; D010507:Periodicity; D010775:Photic Stimulation; D011897:Random Allocation; D013312:Stress, Physiological / Q000503:physiopathology*; D013788:Thalamus / Q000502:physiology*