Slight warming of the spinal cord and the hypothalamus in the pigeon: effects on thermoregulation and sleep during the night

1. 1.|Pegions were chronically implanted with thermodes and thermocouple re-entrant tubes both in the vertebral canal and in the anterior hypothalamus. Arousal states were determined using EEG-, EOG- and EMG-electrodes, and the metabolic rate by measuring O₂ consumption. 2. 2.|During darkness (D), slight warming of the hypothalamus to a temperature level characteristic of light (L) had little or no effect. 3. 3.|Warming the spinal cord to the L-level resulted in a dramatic decrease of the metabolic rate and the extraspinal body temperature. Moreover, warming the spinal cord increased the amount of slow-wave sleep and highly reduced paradoxical sleep. 4. 4.|Our results support the idea of an interdependence between thermal state and arousal state.