antibodies raised against vasoactive intestinal peptide ( vip ) , substance p ( sp ) , somatostatin ( som ) , neuropeptide y ( npy ) , enkephalins ( enk ) and gastrin-releasing peptide ( grp ) were used , and for each of these antisera distinct populations of immunoreactive ( ir ) nerve fibres were observed .
C0003241
antibodies
C0020960
antisera