Direct Stimulation of the Hypoglossal Nucleus by Acetylcholine in Extreme Dilutions

Abstract

Acetylcholine (ACh.), when applied in minute amounts to the eserinized cerebral cortex, induces marked excitatory effects;1 it was inferred that the ACh. stimulates or facilitates various cortical synapses. The experiments here reported indicate that ACh., on direct application in extreme dilutions, stimulates a motor nucleus, namely the hypoglossal nucleus; this nucleus is readily accessible, as the trigonum hypoglossi, immediately beneath the floor of the fourth ventricle.2Methods. Decerebration under ether was by the Sherrington decerebrator. Both common carotids were tied or, in other experiments, both internal carotids were tied and also the branches of external carotids, but leaving lingual arteries intact; essentially similar results were obtained in both preparations. The skull was held in a special clamp, so that the entire tongue could be observed. The floor of fourth ventricle was exposed by removing median parts of cerebellum. Acetylcholine chloride (ACh. Cl) (Merck) was dissolved in buffered ...