Alterations in GAP-43-immunoreactive innervation in the aging rat pituitary.
The levels and distribution of the growth-associated protein, GAP-43, were examined in the pituitary glands of young and aging Sprague-Dawley rats, using immunohistochemical techniques on tissue sections and Western blot analyses. GAP-43-immunoreactive innervation was observed in sections in the intermediate and neural lobes of animals aged 8-15 months, while in the oldest rats studied (17 months), stained fibers were observed mainly in the neural, but not the intermediate lobe. Western blots revealed reduced levels of GAP-43 in samples from 15 month old animals, as compared to 12 month old rats, in the neurointermediate lobes. There was no immunoreactivity for GAP-43 in the anterior lobes in the tissue sections or in the blots in any of the glands examined. A diminished level of GAP-43 in pituitary innervation in aged animals suggests a reduced ability for nerve terminals to undergo 'plastic' changes in their relationship to target endocrine cells. Since GAP-43 has also been suggested to modulate neurotransmitter release, a reduction in the protein in aging nerve terminals may diminish availability of transmitters at presynaptic sites.
Saland
L C
LC
Department of Anatomy, University of New Mexico School of Medicine, Albuquerque 87131-5221, USA. lsaland@medusa.unm.edu
Perrone-Bizzozero
N I
NI
Sower
A
A
Samora
A
A
Ramirez
D
D
Apodaca
A
A
D000375:Aging / Q000502:physiology*; D000818:Animals; D000918:Antibody Specificity; D015153:Blotting, Western; D019922:GAP-43 Protein; D007150:Immunohistochemistry; D008297:Male; D008562:Membrane Glycoproteins / Q000032:analysis / Q000276:immunology*; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000276:immunology*; D016900:Neurofilament Proteins / Q000032:analysis / Q000276:immunology*; D010902:Pituitary Gland / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley
D019922:GAP-43 Protein; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D016900:Neurofilament Proteins