Relative to the analgesic action of vanilline and salicylaldehyde reported by Prof. Tsunoo, there are numerous points to be investigated and traced, which are left untouched, in the phases of its mechanism of action. In the present paper, the author deals exclusively with the local anaesthetic action of aromatic aldehydes specifically of vanilline. As the control substance for vanilline, cocain was employed, and as aldehydes, salicylaldehyde in addition to vanilline were selected. As furan compounds, furfurol, oxymethylfurfurol, acetyioxymethylfurfurol, di- (furfurol-methy1-2) -ether, etc. were employed for the experiments. In author's Department, glycocoll and taurin were frequently used for the studies on vanillin in the past; therefore, histidin and isoserin was also included. As aminosulfonic acid of taurin series, L-amino-2-oxypropansulfonic acid, 1-pyridy1-2-oxypropansulfonic acid, benzoylaminooxypropan-fulfonic acid, and as a special case, taurocholic acid were included. Excepting taurin and isoserin, the above three derivatives of aminosulfonic acid possess OH-radical in their molecules; therefore, the author considered that they might affect the local anaesthetic action of vanilline. As the control substance for aldehydes, vanillic acid, oxymethylpromucinic acid and bis- (carboxyfuran) -methylether were added.
1) In the application of vanilline alone, the anaesthetic action in the rabbit cornea could not be recognized, but it faintly enhanced the same action of cocain.
2) In the applications of vanilline combined with taurin, glycocoll, taurocholic acid, aminooxypropansulfonic acid and its derivatives and histidin respectively, the anaesthetic action of vanilline in the cornea did not appear.
3) The anaesthetic action of vanilline in the surface of the leg of frog exceeds that of cocain.
4) In the combined application of vanilline with equal mol of cocain, the surface anaesthetic action was enhanced, but no enhancement was recognized in the combination with 2 mol of cocain.
5) In the combined application of vanilline with equal mol of procain, the surface anaesthetic action was reduced. Probably, this is due to the inactivation of CHO-radical, which is the active atomic group in the molecule of vanilline, as a result of chemical reaction between vanilline and cocain or procain.
6) In the combined application of vanilline with taurin or glvcocoll, the surface anaesthetic action was enhanced.
7) The surface anaesthetic action of furfurol, oxymethylfurfurol, and acetyloxymethylfurfurol was intense.
8) The paralytic action of vanilline to the motorial fibers of sciatic nerve of frog was much more intense compared with that of cocain. Furf urol and acetyloxymethylf urfurol also demonstrated an intense action.
9) The anaesthetic action of vanilline to the sensory fibers of sciatic nerve of frog was much more intense compared with that of cocain. The action of salicylaldehyde was even further more intense.
10) The combination with oxyamino acids or oxyaminosulfonic acids such as isoserin, aminooxypropansulfonic acid, benzoylaminooxypropansulfonic acid and pyridyloxypropansulfonic acid did not generally affect the local anaesthetic action of vanilline.
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