title: Deafferentation removes calretinin immunopositive terminals, but does not induce degeneration of calbindin D-28k and parvalbumin expressing neurons in the hippocampus of adult rats.
abstract: Unilateral combined transections of the fimbriafornix and angular bundle in adult Fischer 344 rats were used to study the effects of deafferentation on hippocampal expression of calretinin, calbindin D-28k, and parvalbumin. Reflecting the widespread degeneration of synaptic contacts, immunostaining for glial fibrillary acidic protein 6 days after the lesions was increased in lacunosum-molecular and oriens layers of CA1, 2, and 3 in ipsi- and contralateral hippocampus and in the ipsilateral dentate gyrus outer molecular layer. At 21 days the immunoreactivity had decreased to control levels except for a still slightly increased signal in the oriens layer of CA1-3. At 6 and 21 days after the combined lesions the numbers of hippocampal neurons containing calretinin, parvalbumin, and calbindin D-28k was unaltered. The combined lesions abolished calretinin containing terminals in the dentate gyrus inner molecular layer on the deafferentated side. This could be reproduced by single unilateral fimbria-fornix transections, suggesting that the axons of these calretinin positive terminals project to the hippocampus through the fimbria-fornix. The most likely origin of the calretinin positive terminals are neurons in the supramammillary hypothalamic nucleus. Our findings demonstrate that the extensive lesion-induced synaptic rearrangements in the adult hippocampus do not induce degeneration of hippocampal neurons expressing calretinin, calbindin D-28k, and parvalbumin, but do remove calretinin containing terminals which reach their targets in the hippocampus through the fimbria-fornix.
authors.affiliation: Division of Neurogerontology, Andrus Gerontology Center, University of Southern California, Los Angeles.
authors.forename: K D
authors.initials: KD
authors.lastname: Beck
authors.forename: F
authors.initials: F
authors.lastname: Hefti
authors.forename: H R
authors.initials: HR
authors.lastname: Widmer
mesh_terms: D000818:Animals; D064032:Calbindin 2; D064026:Calbindins; D003714:Denervation; D005904:Glial Fibrillary Acidic Protein / Q000276:immunology / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D009410:Nerve Degeneration / Q000502:physiology; D009411:Nerve Endings / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009475:Neurons, Afferent / Q000502:physiology*; D010320:Parvalbumins / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*
chemical_list: C576512:Calb2 protein, rat; D064032:Calbindin 2; D064026:Calbindins; D005904:Glial Fibrillary Acidic Protein; D009419:Nerve Tissue Proteins; D010320:Parvalbumins; D064030:S100 Calcium Binding Protein G