Responses of single taste fibers and whole chorda tympani and glossopharyngeal nerve in the domestic pig, Sus scrofa

Whole nerve, as well as single fiber, responses in the chorda tympani prope r (CT) and glossopharyngeal (NG) nerves of 1- to 7-week-old pigs were recor ded during taste stimulation. In the CT acids and in the NG bitter compound s gave the largest responses. Both nerves exhibited large responses to mono sodium glutamate (MSG), MSG with guanosine 5'-monophosphate (GMP) and MSG w ith inositine 5'-monophosphate (IMP) as well as to glycine, xylitol, sucros e, fructose and glucose. Alitame, aspartame, betaine, neohesperedin dihydro chalcone (NHDHC), super-aspartame, saccharin and thaumatin elicited no or l ittle response. Hierarchical cluster analysis of 49 CT fibers separated fou r major clusters. The M cluster, comprising 28.5% of all fibers, is charact erized by strong responses to MSG, KCl, LiCl and NaCl. The responses to NaC l and LiCl were unaffected by amiloride. The H cluster (24.5%) includes uni ts responding principally to acids. The Q cluster (18.5%) responds to quini ne hydrochloride (QHCl), sucrose octaacetate (SOA) and salts with amiloride . The S cluster (28.5%) exhibits strong responses to xylitol, glycine and t he carbohydrates as well as to MSG alone and to MSG with GMP or IMF. In 31 NG fibers, hierarchical cluster analysis revealed four clusters: the M clus ter (10%), responding to MSG and MSG with GMP or IMP; the H cluster (13%), responding to acids; the Q cluster (29%), responding strongly to QHCl, SOA and tilmicosin(R); and the 5 cluster (48%), responding best to xylitol, car bohydrates and glycine but also to the umami compounds. Multidimensional sc aling analysis across fiber responses to all stimuli showed the best separa tion between compounds with different taste qualities when information from both nerves was utilized.