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Fine structure of rat septohippocampal neurons. III. Recovery of choline acetyltransferase immunoreactivity after fimbria‐fornix transection
Author(s) -
Naumann T.,
Kermer P.,
Frotscher Michael
Publication year - 1994
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.903500202
Subject(s) - axotomy , choline acetyltransferase , biology , fornix , cholinergic , cholinergic neuron , axoplasmic transport , retrograde tracing , neuroscience , apposition , anatomy , central nervous system , hippocampus
Most cholinergic projection neurons in the medial septal nucleus (MS) lose their capability to synthesize choline acetyltransferase (ChAT) after axotomy by bilateral fimbria‐fornix transection. We have recently shown that identified septohippocampal neurons survive axotomy up to 10 weeks and display fine‐structural characteristics of cells in control rats. However, the fate and functional role of these neurons remained unclear. Here we describe observations made in rats which survived axotomy for 6 months. Adult Sprague‐Dawley rats were subjected to bilateral transection of the fimbria‐fornix system. In some animals septochippocampal projection neurons were labeled by the retrograde fluorescent tracer Fluoro‐Gold (FG) prior to axotomy. After varying survival times following fimbria‐fornix transection, the animals were fixed and sections of the septal region immunostained for ChAT. Three weeks postlesion, the number of ChAT‐positive cells in the MS was reduced to 19% of control, suggesting a severe neuronal loss. However, 10 weeks and 6 months after axotomy this value increased to 28% and 54%, respectively. Fine‐structural analysis of ChAT‐postive neurons after 6 months survial revealed all characteristics of vital cells including normal input synapses. The majority of these cells could be identified as former septohippocampal projection neurons by the presence of FG. We conclude that many neurons in the MS have the capacity to restore their transmitter synthesis in a long‐lasting process following axotomy. © Wiley‐Liss, Inc.