| 摘要: | Glutamate stimulation of the dorsal facial area (DFA), an area located just dorsal to the facial nucleus, increases blood flow of common carotid artery (CCA). Nitrergic neurons, which release nitric oxide (NO), are important in cardiovascular regulatory areas. We determined whether the nitrergic neurons might present and play a role in the DFA to regulate CCA flow in chloralose and urethane anesthetized cats. The right femoral artery and vein were cannulated for measurement of arterial blood pressure and fluid supplement, respectively. The CCA flow was measured with a laser Doppler flow-probe. Drugs were microinjected through a three-barrel hypodermic needle inserted into the DFA. Injection of glutamate, L-arginine (a NO precursor) and sodium nitroprusside (a NO donor) caused dose-dependent increases in the CCA flow. The glutamate- or L-arginine-induced flow increase was attenuated by pretreatment with NG-nitro-arginine methyl ester (L-NAME, a non-specific NO synthase inhibitor), 7-nitroindazole (7-NI, a relatively selective nNOS inhibitor), or methylene blue (a guanylate cyclase inhibitor). The L-arginine-induced flow increase was attenuated by GDEE (AMPA receptor antagonist) or D-AP5 (NMDA receptor antagonist). Injection of L-NAME, 7-NI, or methylene blue (a guanylate cyclase inhibitor) decreased basal CCA flow. Histochemical staining with nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d), a maker of NO synthase, demonstrated nitrergic neurons and fibers in the DFA. In conclusion, nitrergic neurons and fibers (probably presynaptic nerves), which are dependent on NO synthase and guanylyl cyclase mechanisms, are present in the DFA for regulation of the CCA flow; and NO is produced in tonic and involved in releasing glutamate that stimulates the DFA to maintain the basal CCA flow. Key words: carotid artery, cerebral blood flow, nitrergic neuron, parasympathetic |
