Immunohistochemical localization and quantification of glial fibrillary acidic protein and synaptosomal-associated protein (mol. wt 25000) in the ageing hippocampus following administration of 5,7-dihydroxytryptamine.
Responses to injury in the ageing hippocampus were assessed utilizing the synaptic markers glial fibrillary acidic protein and synaptosomal-associated protein (mol. wt 25,000) following administration of the neurotoxin, 5,7-dihydroxytryptamine, into the fimbria-fornix and cingulum bundle to denervate serotonergic afferent input to the dorsal hippocampus. Age-dependent alterations in hippocampal immunohistochemical localization of glial fibrillary acidic protein and synaptosomal-associated protein were evaluated in female Fischer 344 rats following serotonergic deafferentation with 5,7-dihydroxytryptamine. Across the lifespan, as indicated by measurements taken at three, 18, 21 and 29 months, marked increases in glial fibrillary acidic protein, but not synaptosomal-associated protein immunoreactivity, occurred throughout the hippocampus at 21 and 29 months compared to three and 18 months. Following three weeks pretreatment with 5,7-dihydroxytryptamine (20 microg total dose) or vehicle (0.1% ascorbic saline; 2 microl total volume) infused in the fimbria-fornix/cingulum bundle, immunohistochemical analysis demonstrated marked increases of glial fibrillary acidic protein, but not synaptosomal-associated protein, in the 18-month 5,7-dihydroxytryptamine group compared to the 18-month vehicle and 3-month 5,7-dihydroxytryptamine groups. Additionally, a significant increase in glial fibrillary acidic protein concentration was found by enzyme-linked immunosorbent assay in the 18-month 5,7-dihydroxytryptamine group compared to the 18-month vehicle and three-month 5,7-dihydroxytryptamine groups. These results demonstrate that selective neurotoxicant damage of the hippocampal serotonergic system differentially alters the expression of glial fibrillary acidic protein. This approach may provide a valuable tool to determine the ability of the hippocampus to respond to age-related neurodegenerative injury.
Dugar
A
A
Department of Pharmacology, The Pennsylvania State University College of Medicine, Hershey 17033-0850, USA.
Patanow
C
C
O'Callaghan
J P
JP
Lakoski
J M
JM
D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology*; D000375:Aging / Q000378:metabolism*; D000818:Animals; D005260:Female; D005625:Frontal Lobe / Q000187:drug effects / Q000378:metabolism; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism*; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D007150:Immunohistochemistry; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D018490:Serotonin Agents / Q000494:pharmacology*; D050825:Synaptosomal-Associated Protein 25; D014018:Tissue Distribution
D005904:Glial Fibrillary Acidic Protein; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D018490:Serotonin Agents; C494210:Snap25 protein, rat; D050825:Synaptosomal-Associated Protein 25; D015116:5,7-Dihydroxytryptamine