Comparison of Adrenergic Activation by Anticholinesterases and by Hypoxia

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Abstract
The hypertensive response to eserine in the rat is accompanied by an increase in lung resistance to inflation. Usually, these two effects do not occur simultaneously. The effects of acute hypoxemia on the blood pressure of the rat were found to be variable, ranging from a biphasic effect to a pure hypertension or hypotension. Inhalation of 11 per cent oxygen in nitrogen produced only a fall of blood pressure. Bretylium was found to block the hypertensive response to eserine, while leaving intact the effect of eserine on the bronchi. On the other hand, bilateral vagotomy was found to block the effect of small doses of eserine on the bronchi and not to affect the blood pressure response to eserine. Neostigmine caused a small rise of blood pressure and a very significant bronchoconstriction. It is concluded that bronchoconstriction and subsequent hypoxia might contribute to the hypertensive response to eserine in the curarized rat, but this mechanism does not seem to be of primary importance for a hypertensive action of eserine.