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Kuo JS, Leung YM, Lin NN, Lee TJ, Gong CL: Nicotine stimulation of the medulla increases blood flow of the common carotid artery in cats. Auton Neurosci. 2010 Jan 15;152(1-2):49-54. Epub 2009 Sep 19.
Microinjection of nicotine or glutamate into the dorsal facial area (DFA) of the medulla increases blood flow of common carotid artery (CCA). Whether there is a causal relationship between these two events is not known. Various agonists and antagonists for the nicotinic and glutamatergic receptors were microinjected through a four-barrel tubing into the DFA of anesthetized cats. Microinjections of nicotine [a non-selective nicotinic acetylcholine receptor (nAChR) agonist], choline (a selective alpha7-nAChR agonist), glutamate or KCl induced a modest increase in CCA blood flow. The nicotine- and choline-induced increases were reduced by alpha-bungarotoxin (an alpha7-nAChR antagonist) as well as MK-801 (a non-competitive NMDA receptor antagonist) or glutamate diethylester (a competitive AMPA/kainate receptor antagonist). The glutamate or KCl-induced increases were blocked by MK-801 and glutamate diethylester, but not by alpha-bungarotoxin. In conclusion, activation of nAChRs primarily via alpha7-nAChR caused a release of glutamate, which in turn activated NMDA and AMPA receptors, while cholinergic substance was not released into the DFA to activate the nicotinic receptor. |
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