The effect of eserine on the response of the vas deferens to hypogastric nerve stimulation.

In experiments in which the vas deferens together with the hypogastric nerve of the guinea-pig was studied as an isolated preparation, the relation between frequency of electrical stimulation of the nerve and the height of contraction was determined. The optimal frequency was 20 shocks/sec. This value was the same when hyoscine was present to exclude the direct effect of any acetylcholine which might be released. When eserine was added to the bath in the presence of hyoscine, the response to stimulation at a frequency of 5 shocks/sec gradually increased until it became many times greater; the response to a frequency of 10 shocks/sec also increased, though to a less extent, but eserine decreased the amplitude of the contraction at a stimulus frequency of 20 shocks/sec. Neostigmine had the same effect as eserine. These findings indicate that, in the presence of hyoscine, eserine increased the noradrenaline released by low frequency stimulation, but decreased it for high frequency. If this is so, the results are compatible with the belief that there is a cholinergic link in the release of noradrenaline by hypogastric nerve stimulation.