Chorda tympani proper nerve responses to intra-arterial and surface stimulation of the tongue in rhesus monkey and rat

The effect of intra-arterial injection of the proteins monellin,thaumatin and miraculin on the activity of the chorda tympaniproper nerve were recorded in the rhesus monkey (Macaca mulatto)and the rat (Sprague–Dawley). The substances were injectedinto the blood stream to the lingual artery. It was found thatmonellin and thaumatin elicited a response only in the monkeyand not in the rat. Acetylated thaumatin, a tasteless substance,gave no increase of the nerve activity. Miraculin had no effectin either species. NaCl, sucrose and citric acid injected intra-arteriallygave a response in both species. It is concluded that the responsesto intra-arterial injections were caused by stimulation of thetaste buds and not nerve fibers. The results suggest there aretaste receptors also on the parts of the taste cells not facingthe oral cavity. The finding that there was no cross-adaptationbetween intra-arterial and oral application supports this conclusion.