with the exception of a small number of double-labeled neurons observed in the periaqueductal gray following injections of fluorescent dyes into the nuclei reticularis paragigantocellularis and gigantocellularis pars alpha , no double-labeled cells were found in this midbrain region following injections of tracers into various combinations of the above 4 nuclear groups .
C0007610
nuclei
C0007634
cells