Objective To observe the connections between enkephalin immunoreactive (ENK-ir) terminals and γ-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 d