[The role of medial medulla in the depressive responses in pulmonary and carotid arteries to injection of acetylcholine at fourth ventricle].
The role of medial medulla in the depressive responses in pulmonary and carotid arteries to injection of acetylcholine (ACh) at the fourth ventricle was studied by means of electrolytic destruction and microinjection of drugs at the relevant brain areas. It was found that (1) electrolytic destruction of medial medulla significantly diminished the depressive responses to ACh in pulmonary and carotid arteries; (2) destruction of nucleus tractus solitarius (NTS) at the level of the medullary obex did not affect the depressive responses in both arteries; obex did not affect the depressive responses in both arteries; (3) microinjection of 5-hydroxytryptamine (5-HT) blockers, cyproheptadine and 2-bromolysergic acid diethylamide (BOL), into the fourth ventricle or medial medulla could lessen the depressive responses to ACh in pulmonary and carotid arteries; (4) microinjection of naloxone in the same way could partially abolish the depressive responses. It is thus assumed that the ACh-induced depressive responses in pulmonary and carotid arteries are associated with the structural integrity of the medial medulla but not related to the central projection area of the buffer nerves. Therefore, the depressive responses in pulmonary and carotid arteries initiated by injection of ACh at the fourth ventrical are mediated by activating the 5-HT and endorphin systems of the medial medulla which in turn inhibits the tonic activities of the sympathetic preganglionic neurons in the spinal cord.
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D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002339:Carotid Arteries / Q000502:physiology; D003864:Depression, Chemical; D005260:Female; D007276:Injections, Intraventricular; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D011651:Pulmonary Artery / Q000502:physiology; D011817:Rabbits
D000109:Acetylcholine