Effects of medullary administration of a nitric oxide precursor on cardiovascular responses and neurotransmission during static exercise following ischemic stroke

We have reported that in rats with a 90 min left middle cerebral artery occlusion (MCAO) and 24 h reperfusion, pressor responses during muscle contractions were attenuated, as were glutamate concentrations in the left rostral ventrolateral medulla (RVLM) and left caudal VLM (CVLM), but gamma-aminobutyric acid (GABA) levels increased in left RVLM and CVLM. This study determined the effects of l-arginine, a nitric oxide (NO) precursor, within the RVLM and (or) CVLM on cardiovascular activity and glutamate/GABA levels during static exercise in left-sided MCAO rats. Microdialysis of l-arginine into left RVLM had a greater attenuation of cardiovascular responses, a larger decrease in glutamate, and a significant increase in GABA levels during muscle contractions in stroke rats. Administration of NG-monomethyl-l-arginine, an NO-synthase inhibitor, reversed the effects. In contrast, l-arginine administration into left CVLM evoked a greater potentiation of cardiovascular responses, increased glutamate, and decrea...