Effects of glutamate and aspartate on sympathetic preganglionic neurons in the upper thoracic intermediolateral nucleus of the cat.

Glutamate and aspartate excited all spontaneously active sympathetic preganglionic neurons (SPNs) tested in the intermediolateral nucleus of spinal segments T1-T3. Most silent neurons could be induced to discharge but the remainder showed only a decrease in antidromic spike amplitude. These effects were typically fast (on, off less than 1 s). D,L-Homocysteic acid also produced excitation; this effect was typically slower. Glutamate and aspartate were usually equipotent; 20% were differentially sensitive to aspartate, 10% to glutamate.