ABSTRACT
Objective To observe the connections between enkephalin immunoreactive(ENK-ir) terminals and ?-aminobutyric acid immunoreactive(GABA-ir) neurons in the rostral portion of the nucleus tractus solitarious(rNTS) of the rat. Methods Double-immunofluorescent labeling method and the pre-embedding immunohistochemical staining combined with immuno-gold particles labeling technique for electron microscopic detection were used in the present study. Results Under the laser scanning confocal microscope,dense ENK-ir fibers and terminals and some GABA-ir neurons were observed in the rNTS.Close contacts between ENK-ir terminals and GABA-ir cell bodies were also detected.By using the electron microscopic technique,ENK-ir reaction products were found to be mainly localized on the surface of round clear vesicles and dense-cored vesicles in the axon terminals.ENK-ir terminals formed symmetric,which was a dominant pattern,and asymmetric synaptic connections with GABA-ir and immunonegative cell bodies and dendrites.Conclusion The ENK-ir terminals might take part in the transmission and regulation of the taste information in the rNTS through inhibiting,exciting the GABAergic neurons or inhibiting directly the activity of neurons within the rNTS.