Met-enkephalin-Arg6-Gly7-Leu8-like immunoreactivity in mammalian taste buds

Light-microscopic immunocytochemistry for various bioactive peptides including some gastroenteropancreatic hormones and a neuronal enzyme, neuron-specific enolase (NSE), was applied to taste buds in the circumvallate papillae of rats, mice and guinea pigs. In all the species positive immunoreactivities were demonstrated for Met-enkephalin-Arg6-Gly7-Leu8 (Met-Enk-8). The Met-Enk-8-like immunoreactivity was confined to parts of the spindle-shaped bud cells. These cells in rats and guinea pigs displayed a concomitant immunoreactivity for NSE. In the mouse taste buds, however, there appeared no such correlation between the immunoreactivities. Considering our previous data, the present finding supports a possibility that opioid peptide(s) derived from preproenkephalin A might be the transmitter(s) of the gustatory cell.