Evidence that adrenaline neurons in the rostral ventrolateral medulla have a vasopressor function.

Focal electrical or chemical stimulation in the rostral ventrolateral medulla of the rat and rabbit evoked large increases in arterial pressure when the stimulus sites were in the region containing a high density of adrenaline synthesizing neurons, but much smaller or no responses when the sites were outside this region. The adrenaline neurons were identified in the rat by an immunohistochemical procedure, and in the rabbit by a modification of the FAGLU catecholamine fluorescence method. By combining the fluorescence procedure with the method of retrograde transport of horseradish peroxidase, many of the adrenaline synthesizing neurons in the rabbit were shown to project to the spinal cord.