Neuropeptide Y inhibits the hyperexcitability of type A neurons in chronically compressed dorsal root ganglion of the rat.

Our recent data revealed adrenergic sensitivity in chronically compressed dorsal root ganglion (DRG) of rats. As neuropeptide Y (NPY) is a common sympathetic co-transmitter, we investigated the effect of NPY on injured DRG neurons. The expression of NPY Y1 and Y2 receptors and the effect of NPY on chronically compressed DRG neurons were studied using in situ hybridization and extracellular single fiber recording in vitro, respectively. After DRG compression, the expression of Y1 receptor was distinctly increased in large and medium-sized DRG neurons, while Y2 receptor was increased in small DRG neurons. NPY inhibited both the spontaneous activity and the excitatory effect of norepinephrine in injured DRG A-neurons. The results suggest a possibility that NPY may inhibit the hyperexcitability of injured DRG A-neurons via increased Y1 receptor following chronic compression.