Chemical stimulation of the nerve cord of Cambarus clarkii

Abstract

A preparation of the central nervous system of crayfish was made by decapitating the animal and uncovering the nerve cord of the posterior abdominal segments. Application of a stimulating substance to this portion of the cord resulted in convulsive movements of the thoracic appendages. Stimulation was obtained from application of excitants of the first class, BaCl₂, KCl, Na₃ citrate, in concentrations isosmotic with the animal's blood. Tetraethylammonium chloride in M/64 concentration acted as a strong excitant. Of the excitants of the second class, camphor, strychnine, atropine, picrotoxin, nicotine, caffeine and phenol were active. Creatine alone showed no effect. The central nervous system of Cambarus therefore differs from that of Lumbricus 1 in being sensitive to the action of nicotine, phenol and caffeine. The two forms are alike in being insensitive to creatine, and in the fact that the latent period for chemical stimulation is very short, less than a minute.