Differential distribution in rat basal ganglia of Met-enkephalin- and Met-enkephalin Arg6 Phe7-like peptides revealed by immunohistochemistry.

Antisera to Met-enkephalin and its heptapeptide variant Met-enkephalin Arg6Phe7 were used in immunohistochemistry to study distribution of immunoreactive material in rat basal ganglia. In the pallidum, the Met-enkephalin antiserum, but not the Met-enkephalin Arg6Phe7 antiserum, revealed abundant nerve terminals, whereas in the caudate-putamen the heptapeptide antiserum demonstrated numerous immunoreactive cell bodies that were not shown by the Met-enkephalin antiserum. The differential distribution of immunoreactivity is compatible with distinct physiological roles for the two peptides in basal ganglia.