Relationship between neuronal activity and brain temperature in rats.
Warming of a brain area in a behaving rat may reflect a local increase in neuronal activity, or the heat may be supplied from peripheral organs (muscles) via the arterial blood. To investigate the role of neuronal activity, brain temperature was measured in the hippocampus of anaesthetized rats in response to intense and prolonged stimulation of the perforant path. Repetitive discharge induced by such stimulation failed to raise dorsal hippocampal temperature by more than 0.6 degree C, even if cells discharged throughout the train. The widespread neuronal activity during paradoxical sleep was equally ineffective (increases < 0.3 degree C). Thus, most of the heat producing an increase in brain temperature during behaviour probably arises from peripheral organs.