ABSTRACT
It has been reported that the small type of neurons in the dorsal root ganglion (DRG) play an important role in pain regulation by a presynaptic mechanism via the metabotropic type-B γ-aminobutyric acid receptors ( GABABR ). In order to understand whether the 2populations of the small type of the neurons, peptidergic and nonpeptidergic, in DRG share the same role, immunoflourescent histochemical methods and confocal laser scanning microscope were employed to investigate the expression of the GABABR in the peptidergic and nonpeptidergic small DRG neurons. The results revealed that 92% of the peptidergic and 90% of nonpeptidergic small DRG neurons express GABABR in their perikarya and central processes, which distribute in the various laminae of the spinal dorsal horn. These results suggest both the peptidergic and nonpeptidergic populations of the small neurons in the DRG share similar role in pain modulation via presynaptic mechanisms but in given laminae of the spinal dorsal horn.