Responses of single units in the midline medulla to stimulation of the rostral ventrolateral medulla.

Single units in the midline medulla were characterized as sympathoexcitatory (SE), sympathoinhibitory (SI) or serotonin (5-HT) neurons. Post-stimulatory changes in the firing patterns of sympathoexcitatory, sympathoinhibitory and 5-HT units were observed during single shock stimulation of the pressor area of the rostral ventrolateral medulla (RVLM). Excitation, inhibition, or no change in cell firing patterns were observed for each cell type, but each cell showed only one type of response to stimulation. No midline neurons were antidromically activated by stimulation of the rostral ventrolateral medulla. These results are discussed in relation to neuronal pathways between the RVLM and the midline medulla involved in the generation of sympathetic activity.