Effect of Cerebral Ablation on a Circadian Pituitary Adrenocorticotropic Rhythm in C Mice

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Abstract
The ACTH content of pituitary glands from intact or starved Bagg albino (C) strain mice undergoes a circadian rhythm which persists after suprathalamic brain ablations with a significant amplitude and a grossly unaltered internal timing in relation to the corticosterone rhythm in serum. Hence, the cerebral cortex of the mouse as well as number of subcortical structures, including the limbic system, are dispensable for the short-term persistence of a rhythm in pituitary ACTH content. More extensive brain ablations, including, inter alia, the removal of the thalamus and the hypothalamus interfere with the demonstration of a circadian rhythm in pituitary ACTH content—when this rhythm must be evaluated as a so-called group phenomenon, i.e., on the basis of data from separate groups of presumably comparable animals, rather than by evaluating a given individual repeatedly over an apropriate period. The different temporal behavior of pituitary ACTH content observed in the group with suprapontine brain ablations might result from circadian desynchronization. (Endocrinology 76:895, 1965)