Effects of eserine and acetylcholine on the respiratory centers and hypoglossal nuclei.

Abstract

The floor of the fourth ventricle is exposed in the cat, decerebrated with the Sherrington Decerebrator. Eserine, 0.15 mgm. per kgm. body weight intravenously, induces extra respirations and tongue retractions, the latter at the same rate as, and slightly preceding, the "original" respirations. Tongue retractions are caused by irradiation from inspiratory centers to hypoglossal nuclei. Acetylcholine (ACh) concentrations of 1:5 × 107 to 1:106, applied in a small rectangle of spot test paper to the floor of fourth ventricle, enhance respiratory and lingual effects; these concentrations of ACh or, occasionally, up to 1:5 × 104 often induce convulsive discharges from hypoglossal nuclei, as shown by powerful tongue contractions. Effects of eserine on respiration are not due to concurrent blood pressure changes, which are insignificant. Intravenous eserine and medullary ACh are believed to stimulate and facilitate various central synapses; both drugs stimulate the inspiratory centers. Medullary ACh excites particularly the eserinized synapses surrounding the motoneurones of the hypoglossal nuclei, thus inducing the convulsive discharges from these nuclei. Effects of eserine and ACh are abolished and precluded by intravenous atropine, results that are in harmony with those of several recent investigators.