Nicotine stimulation of the medulla increases blood flow of the common carotid artery in cats.
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.
Kuo
Jon-Son
JS
Neuro-Medical Scientific Center and Center for Vascular Medicine, Buddhist Tzu Chi General Hospital and Tzu Chi University, Hualien, Taiwan.
Leung
Yuk-Man
YM
Lin
Nai-Nu
NN
Lee
Tony Jer-Fu
TJ
Gong
Chi-Li
CL
D000818:Animals; D017536:Carotid Artery, Common / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D002415:Cats; D002794:Choline / Q000008:administration & dosage / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D018698:Glutamic Acid / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology; D006439:Hemodynamics / Q000187:drug effects; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects* / Q000502:physiology; D008845:Microinjections; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000008:administration & dosage / Q000493:pharmacokinetics*; D018733:Nicotinic Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D020033:Protein Isoforms / Q000819:agonists; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors; D018092:Kainic Acid Receptors / Q000037:antagonists & inhibitors; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D012039:Regional Blood Flow / Q000187:drug effects* / Q000502:physiology; D013268:Stimulation, Chemical
D002794:Choline; D018698:Glutamic Acid; D009538:Nicotine; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D020033:Protein Isoforms; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate