Cardiovascular effects of nitric oxide and N-methyl-D-aspartate receptors in the nucleus tractus solitarii of rats.
Nitric oxide (NO) is an endogenously synthesized effector molecule that acts as a neurotransmitter with novel properties in both the central and peripheral nervous systems. We previously reported that NO was involved in central cardiovascular regulation and modulated the baroreflex in the nucleus tractus solitarii (NTS) of rats. The aim of the present study was to determine whether NO and excitatory amino acids reciprocally release each other in the NTS. In normotensive Sprague-Dawley rats, intra-NTS microinjection of L-arginine (1 to 100 nmol/60 nL) produced a dose-dependent decrease in blood pressure and heart rate. Microinjection of excitatory amino acids L-glutamate and NMDA also produced depressor and bradycardic effects. These effects of L-glutamate or NMDA were blocked by prior administration of NO synthase inhibitor N(G)-methyl-L-arginine or N(G)-nitro-L-arginine methyl ester. Similarly, prior administration of N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 and non-NMDA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione significantly attenuated the depressor and bradycardic effect of L-arginine. These results demonstrated a reciprocal attenuation of NO synthase inhibitor and NMDA receptor antagonist on NMDA and L-arginine responses, respectively, in the NTS and suggest that NO and NMDA receptors may interact in central cardiovascular regulation.
Lo
W C
WC
Department of Medical Education and Research, Veterans General Hospital-Kaohsiung, Taiwan, Republic of China.
Lin
H C
HC
Ger
L P
LP
Tung
C S
CS
Tseng
C J
CJ
D000818:Animals; D001120:Arginine / Q000008:administration & dosage / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D001931:Brain Mapping; D001933:Brain Stem / Q000187:drug effects / Q000502:physiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects*; D008297:Male; D008845:Microinjections; D016202:N-Methylaspartate / Q000008:administration & dosage / Q000494:pharmacology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000502:physiology*; D017552:Solitary Nucleus / Q000187:drug effects / Q000502:physiology*; D019323:omega-N-Methylarginine / Q000494:pharmacology
D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; D016194:Receptors, N-Methyl-D-Aspartate; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D018698:Glutamic Acid; C056723:FG 9041; D016202:N-Methylaspartate; D001120:Arginine; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester