Abstract
Intravemioums injections of 5-10 µg/kg of histamine and of 25-50 µg/kg of pilocarpine into spinal cats cause a secondary rise of blood pressure. This pressor response was found to be modified by substances which (a) modify the ganglionic actions of histamimue and pilocarpine (nicotine, tetramethylammonium, TMA), (b) interfere with the liberation of sympathin from the endings of adrenergio fibers (choline 2:6-xylyl ether bromide, TM 10; morphine; methadone), and (c) deplete the peripheral norepinephrinee stores (reserpine).
Thue results inohicate that histamine causes a pressor response in the cat by acting mainly on the adrenal medulla, and that the small pressor respomise of adrenalectomized preparations is due to general stimulation of sympathetic ganglia. Pilocarpine has only a very weak action on the adrenal medulla and acts mainly on sympathetic ganglion cells.
The pressor response to histamine and pilocarpine differs pharmacologically from that to tyramine.
Footnotes
- Received June 4, 1960.
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