TRANSITORY NORADRENERGIC AND PEPTIDERGIC NERVES IN THE CAT KIDNEY

Indirect immunohistochemical methods were used to visualize nerves imm unoreactive for tyrosine hydroxylase (TH), dopamine beta hydroxylase ( DBH), neuropeptide Y, (NPY) and calcitonin gene-related peptide (CGRP) in sections of the kidneys of cats of different ages. Nerve terminals immunoreactive for TH, DBH and NPY innervated interlobar veins and th e renal arterial tree including medullary vascular bundles of cats of each age studied. Most nerve terminals immunoreactive for CGRP innerva ted interlobar arteries. In kidneys of cats 2 to 10 weeks old, TH- and DBH-immunoreactive axons formed elaborate plexuses that were distribu ted throughout much of the outer two thirds of the inner medulla. Inne r medullary NPY-immunoreactive nerve terminals formed sparse plexuses by comparison, thus suggesting a large population of TH-immunoreactive nerve terminals not immunoreactive for NPY. Plexuses immunoreactive f or CGRP also innervated the inner medullae of young cats. Some inner m edullary axons appeared degenerate in 8 and 10 week old cats, and no i nner medullary nerve terminal plexuses were visualized in 12 week old or adult cats. Cen death or paring of axons resulting from mechanisms intrinsic to the neuronal population or from a change in trophic facto rs secreted or expressed by cells in the medulla may effect the loss o f inner medullary nerve terminals in the kidneys of young cats.