Preliminary studies on GABA-immunoreactive neurons in the rat trigeminal ganglion

GABA-immunoreactive (ir) primary sensory neurons have been reported in many studies. However, the role of GABA in the primary sensory neurons and their targets is quite open to question. The present study aimed to examine the GABA-ir neurons in the rat trigeminal ganglion (TG), for the first step of functional study on them. Some neurons in the TG showed GABA-ir, which were ranged from large to small size. The total number of examined TG neurons from 6 ganglia was 2,531, of which 462 neurons (18.3%) showed GABA-ir the large subpopulation of GABA-ir TG neurons is likely to involve in nerve-muscle functions, whereas medium and small subpopulations might participate in cutaneous nociceptive sensory function. The present findings demonstrated a considerable number of sensory neurons containing GABA in the rat TG. Functional studies on GABA-ir neurons in the TG would be an interesting and important issues in future studies. The next aim of our study is to examine the size distribution of GABAergic neurons and the coexistence with other neurotransmitters in the rat TG.