Potentiation by Anticholinesterases of the Response of Rat Mesenteric Arteries to Sympathetic Postganglionic Nerve Stimulation

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Abstract
The anticholinesterase agents, physostigmine, neostigmine, and diisopropylfluorophosphonate were studied for their effect on the vasoconstrictor responses of perfused mesenteric arteries of rat produced by stimulation of their sympathetic postganglionic nerves. The experiments were performed at 30°C. All three anticholinesterase drugs greatly potentiated the vasoconstrictor response to nerve stimulation at a frequency of 1/sec, increased it less at a frequency of 2/sec, and still less at a frequency of 3/sec. At a frequency of 6/sec, there was practically no increase. The infusion of physostigmine potentiated slightly the response to injected norepinephrine, whereas the infusion of neostigmine or diisopropylfluorophosphonate did not alter the response to injected norepinephrine. The increase in response to adrenergic nerve stimulation produced by anticholinesterase agents was interpreted to be due to the inactivation of cholinesterase, thereby causing an increased accumulation of acetylcholine which in turn liberated more norepinephrine from the sympathetic postganglionic fibers.