Identification of diencephalic and brainstem cardiorespiratory areas activated during exercise.

The purpose of this study was to identify diencephalic and brainstem sites active during exercise (EX) in conscious rats running on a treadmill. Brain areas active during exercise, compared to rest conditions (non-EX), were identified using immunocytochemical labelling of the protein product of the proto-oncogene c-fos. Increased labelling was observed in the 'defence area' or 'hypothalamic/subthalamic locomotor regions' including the posterior and lateral hypothalamic areas. Increased labelling with EX was found in both colliculi, the periaqueductal gray matter, the parabrachial complex and the cuneiform nucleus ('mesencephalic locomotor region'). Increased labelling with EX was also found in the medial portion of n. tractus solitarius, and both the rostral and caudal ventrolateral medulla. Conspicuous by an absence of labelling during EX were cells in thalamic areas associated with somatosensory function, although the dorsal column nuclei were also labelled above control. Thus, areas in which labelling was increased during exercise closely correlate with the brain areas which have been implicated in both autonomic and somatomotor control. These results from awake, exercising rats support those obtained previously in anesthetized animal preparations.