Identification of cardiovascular cell groups in the brain stem.

There is now good evidence that there are several distinct groups of cells in the brain stem that are capable of inducing marked changes in cardiovascular function. This paper briefly reviews the results of recent experiments which have identified cardiovascular cell groups in the rostral ventrolateral and dorsomedial medulla, and in the periaqueductal grey and ventral tegmentum of the midbrain. Results of our experiments as well as those of others suggest that excitation of cardiovascular cell groups in the lower brain stem leads to an undifferentiated generalized increase or decrease in sympathetic activity, whereas excitation of certain midbrain cell groups can evoke a highly co-ordinated pattern of autonomic and respiratory changes that closely resembles the pattern associated with certain behaviours in the conscious animal.