The distribution of neuropeptides in the ocular tissues of several mammals: a comparative study.

1. The distribution of several neuropeptides (vasoactive intestinal peptide, substance P, somatostatin and neurotensin) was assessed in ocular tissues from the cow, sheep, rabbit and rat. 2. Vasoactive intestinal peptide was most abundant in the choroid and sclera in all species except the rat. Substance P was most abundant in the retina of cow and rat and in the iris/ciliary body of sheep and rabbit. Somatostatin and neurotensin were most abundant in the retina of all species examined. 3. Regulatory peptides thus display distinct regional distributions within the ocular tissues of a single species of mammal and, in addition, exhibit interspecific variation.