[Effects of microinjection of L-arginine into the depressor area of ventral surface of medulla oblongata on cardiovascular responses].

AIM

To study the effects of L-arginine, a precursor for the synthesis of nitric oxide, when it was microinjected into the functionally identified depressor area in ventral surface of medulla oblongata (VSMd) on cardiovascular responses.

METHODS

Artery pressure (AP), perfusion pressure of the kidney (PPK) and heart rate were recorded to study the effects of microinjection of NO related drugs into VSMd.

RESULTS

(1) Unilateral microinjection of L-arginine (60 - 100 nmol) into VSMd produced prominent dose-related pressor effect and increased PPK but without significant changes in heart rate. (2) Microinjection of L-Arg (100 nmol) 3 min after microinjection of methylene blue (10 nmol) into VSMd did not significantly change AP and PPK. (3) Unilateral microinjection L-glutamate (350 nmol) into VSMd elicited depressor effect (-34.97% +/- 4.33%). The depressor effect was significantly dosed related attenuated by prior microinjection L-arginine (60 - 100 nmol) into the same area.

CONCLUSION

These results suggest that the L-arginine - NO pathway in the VSMd participate in the central regulation of artery pressure and the pathway may have a key role in inhibiting glutamatergic neurotransmission in the anesthetized rats.