Objective: To determine whether there are some differences between GABAA and GABAB receptors in the regulation of cardiovascular activity in the nucleus tractus solitarii(NTS). Methods: Techniques of microinjection into NTS and lesion of NTS as well as electric stimulation of hypothalamic defense area(HDA) were used, and mean arterial pressure(MAP) and heart rate were measured.Results: GABA uptake inhibitor nipecotic acid-induced increase of MAP was blocked by GABAA receptor antagonist bicuculline, but not by GABAB antagonist CGP 35348; glutamate could only partially reverse muscimol-induced elevation of BP while showed no obvious effect on GABAB receptor excitant-induced elevation of BP; and microinjection of bicuculline into NTS could block stimulation of HDA-induced pressor response, but CGP 35348 could not. Conclusion: The differences between GABAA and GABAB receptors in the regulation of cardiovascular activity in NTS may be due to the presynaptic distribution of GABAB receptors and postsynaptic exsistence of GABAA receptors in NTS.