Neurophysiological background of central neural cardiovascular-respiratory coordination: basic remarks and experimental approach.

This paper is comprised of a review of past contributions and their theoretical consequences and a presentation of new results in studies of the origin of sympathetic rhythms and tone. Two basic mechanisms are involved: a primary intracentral coupling with the main cardiovascular-respiratory rhythm (MCRR) generator and a secondary reflex coupling. It was found that the activity and rhythms of certain sympathetic efferents, such as the cervical sympathetic, are closely related to the MCRR. Other efferents, such as the renal sympathetics, are loosely linked and follow drives from other circuits in the genesis of their rhythms and tone. New experimental evidence is given that rhythmic and tonic activity in sympathetic nerves originates from several sources. Hence central respiratory-autonomic systems interaction is not explained by simplistic concepts.