[Effect of microinjection of L-arginine into the caudal pressor area of medulla oblongata on cardiovascular responses in rats].

AIM: To study the effect of microinjection L-arginine, a precursor for the synthesis of nitric oxide into the functionally identified caudal pressor area (CPA) in ventral surface of medulla oblongata. METHODS: Artery pressure (AP), renal perfusion pressure (RPP) and heart rate were recorded to study the effects of microinjection of NO related drugs into CPA. RESULTS: (1) Unilateral microinjection of L-arginine (60 - 100 nmol) into CPA produced prominent dose-related depressor and bradycardic effects and reduced renal perfusion pressure. (2) Unilateral microinjection of L-arginine (100 nmol) 3 min after microinjection of methylene blue (10 nmol) into CPA did not significantly change AP and RPP. (3) Unilateral microinjection of L-glutamate (350 nmol) into CPA elicited pressor effect which was significantly dose-related attenuated by prior microinjection of L-arginine (60-100 nmol) into the same area. CONCLUSION: Theses results suggest that L-arginine-NO pathway in the CPA participates in the central regulation of arterial pressure and may have a key role in the inhibiting of glutamatergic neurotransmission in the anesthetized rats.