ABSTRACT
Objective The immunocytochemical localizations of GABA\-A\| and GABA\-B\|receptor in the mesencephalic trigeminal nucleus(Vme) of the rat were examined in order to provide morphological evidence for a possible functional analysis of GABA\|receptor in the transmission and modulation of the orofacial region trigeminal proprioceptive sensory information. Methods An immunocytochemical staining method was used in the present study,and immunostained sections were observed under light microscope. Results Many neuronal cell bodies,fibers and terminals with dense GABA\-A\| and GABA\-B\|receptor\|like immunoreactivity(\|LI) were observed to be localized in Vme,and different subunits of GABA\|receptor\|LI showed the morphological difference in their distribution:1.Immunoreactivity for GABA\-B R1 subunit was intensely distributed in the cell bodies of Vme neurons,whereas the weak immunoreactivity for GABA\-BR2 subunit was only observed in the region surrounding the somata of Vme neurons which showed negative GABA\-BR2\|LI;2.A considerable number of GABA\-A\|like immunoreactive neurons,fibers and terminals were also found in Vme.It was involved four kinds of subunits(?1,?2,?3 and ?).The heavy immunoreactivity for GABA\-AR?1 and GABA\-AR?3 subunits were only seen in the cell bodies of Vme neurons.On the other hand,the immunoreactivity for GABA\-AR?2 and GABA\-AR? subunits was only observed in the fibers and terminals in the region surrounding the somata of Vme neurons,which showed negative immunoreactivity for above subunits;3.Dense GABA\-BR2\|,GABA\-AR?2\| and GABA\-AR?\|LI fibers and terminals surround the somata of Vme neurons,especially for GABA\-AR?2\|LI.Conclusion\ The present results suggest that there are some differences in the distribution of the various subunits of GABA\-A\| and GABA\-B\|receptor in Vme.It is likely that the inhibitory regulation and control effects of GABAergic terminals on the transmission of orofacial region proprioceptive sensory information might be mainly mediated through GABA\-AR?1 and GABA\-AR?3 subunits in somata of Vme neurons.