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 org ans (muscles) via the arterial blood. To investigate the role of neuro nal activity, brain temperature was measured in the hippocampus of ana esthetized rats in response to intense and prolonged stimulation of th e perforant path. Repetitive discharge induced by such stimulation fai led to raise dorsal hippocampal temperature by more than 0.6 degrees C , even if cells discharged throughout the train. The widespread neuron al activity during paradoxical sleep was equally ineffective (increase s < 0.3 degrees C). Thus, most of the heat producing an increase in br ain temperature during behaviour probably arises from peripheral organ s.