Adrenocortical adaptation to chronic intermittent stress in hemispherectomized pigeon

Hemispherectomized pigeons were exposed daily to electrical footshocks delivered for 15 sec, at the same hour, for 8 weeks. Serial blood samples were obtained through a chronic vascular catheter. The adrenocortical response to chronic intermittent stress was measured kinetically at one week intervals. The initial response including several successive peaks of plasma corticosterone progressively adapted: Late peaks disappeared and only the first one subsisted 12-14 min after stressor application; this first peak diminished in magnitude; furthermore, an anticipatory peak occurred, starting 14 min before stress. In pigeons lesioned in the anterior dorsomedial thalamus, the only response to the stressor was of the single peak (12-14 min) type without any development of anticipatory conditioned response. This phenomenon was consistant all over the experimental period. Thalamic-hypothalamic interrelationships may be suggested to provide neuronal loops that underlie the long lasting, pulsatile repetitive components of the adrenocortical response to acute stress and also the adaptative process of such a response to chronic intermittent stress, including a conditioned, anticipatory endocrine activation.