Sympathetic and parasympathetic ganglia express non-NMDA type glutamate receptors: distinct receptor subunit composition in the principle and SIF cells.
The presence of non-NMDA glutamate receptors in the rat sympathetic and parasympathetic ganglia was examined by immunocytochemistry using specific antibodies against AMPA-type excitatory amino acid receptor subunits (GluR1-4). Three kinds of antibodies specific to the GluR1, GluR2 and 3, and GluR4 subunits were used. The superior cervical ganglion and pterygopalatine ganglion were examined as representatives of sympathetic and parasympathetic ganglia. In the superior cervical ganglion, GluR1- and GluR2/3-like immunoreactivity was observed in most principal neurons and SIF cells. In contrast, GluR4-like immunoreactivity was not observed in the principal cells; however, SIF cells exhibited intense immunoreactivity of GluR4. In the pterygopalatine ganglion, the profile of the immunoreactivity was similar to that seen in the superior cervical ganglia. The subunit compositions between the principal cells and SIF cells were different, whereas the compositions in cell species involved in the autonomic ganglia, sympathetic and parasympathetic ganglia were identical. This suggests that glutamate is another important preganglionic transmitter together with acetylcholine, and the responses elicited in the principal cells and SIF cells might be different because of the difference in subunit composition.