Pargyline and naltrexone fail to antagonize the gustatory avoidance response induced by...

The administration of the dopaminergic neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to rats following the consumption of a novel saccharin solution induced a gustatory avoidance response evidenced by a significant decrease in saccharin intake following its representation. Pretreatment with pargyline, an agent which prevents the metabolism of MPTP to the 1-methyl-4-phenylpyridinium ion (MPP+), did not potentiate or antagonize the magnitude of this aversion. Likewise, pretreatment with naltrexone, an opiate antagonist, failed to alter the gustatory avoidance response induced by MPTP. These observations indicate that MPTP is capable of inducing a gustatory avoidance response and that the mechanism mediating this response is not dependent upon the conversion of MPTP to MPP+ and does not involve the opiate receptor.