Glutamate receptors on postganglionic sympathetic axons.

The present study demonstrates that approximately 36% of postganglionic sympathetic axons in gray rami express receptors for the N-methyl-D-aspartate receptor 1 subunit of the N-methyl-D-aspartate receptor and 10% express the glutamate receptor 1 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor. If these receptors are active, glutamate released from primary afferent terminals could activate these receptors resulting in the release of noradrenaline and other substances from postganglionic sympathetic neurons. This interaction would constitute a non-synaptic, sensory-sympathetic, peripheral reflex that might be important in local vascular control and in pain states that have a sympathetic component.