Basal and stress-induced adrenal cortical activities in the chronic thalamic pigeon.

The plasma corticosterone level was determined in chronic thalamic pigeons. Basal resting adrenocortical activity did not show any diurnal variation and kept a steady intermediate level. The peak and nadir in the morning and in the evening were completely suppressed. Neurogenic stress (restraint) resulted in a sharp increase in the plasma corticosterone concentration 15 min after immobilization. This response was as important in magnitude (three-fold the resting level) in thalamic pigeons as in intact birds. These results can be compared with data obtained after complete or partial deafferentation of the hypothalamus, and after hippocampal or archistriate lesions, and are discussed in terms of sleep-walking alternation in these various experimentally-prepared pigeons.