The Journal of Neuroscience, February 1, 2001, 21(3):1047-1055
Elevation of Nerve Growth Factor and Antisense Knockdown of TrkA
Receptor during Contextual Memory Consolidation
Nancy J.
Woolf1,
Amy M.
Milov1,
Erik S.
Schweitzer2, and
Ali
Roghani3
1 Department of Psychology and 2 Brain
Research Institute, University of California at Los Angeles, Los
Angeles, California 90095, and 3 Department of
Pharmacology, Texas Tech University Health Sciences Center, Lubbock,
Texas 79430
We report here a series of experiments establishing a role for
nerve growth factor and its high-affinity receptor TrkA in contextual
memory consolidation. In all experiments, we trained rats in a novel
chamber using tone and shock. Our first experiment revealed that
endogenous nerve growth factor (NGF) increases in the hippocampus at a
critical time during consolidation that occurs 1 week after training.
NGF levels at other intervals (24 hr and 2 and 4 weeks after training)
did not differ from those of naive control animals. In our second
experiment, we blocked effects that NGF has at 1 week after training by
infusing antisense TrkA phosphorothioate DNA oligonucleotide. Reduction
of septohippocampal TrkA receptor expression selectively impaired
memory consolidation for context but not for tone. Animals with
antisense TrkA oligonucleotide infused into the medial septal area or
CA1 of the hippocampus froze less when placed in the training chamber
than did animals infused with inactive randomized oligonucleotide. At 4 weeks after training, antisense TrkA oligonucleotide had no effect on
freezing. Third, we correlated levels of freezing with choline
acetyltransferase (ChAT) and vesicular acetylcholine transporter
(VAChT) immunohistochemistry. Antisense TrkA infused into CA1 of the
hippocampus reduced cell body cross-sectional area for cholinergic
cells in the medial septal area and decreased the density of
hippocampal terminals labeled for ChAT and VAChT proteins. Cholinergic
cell body measurements were significantly correlated with freezing.
Taken together, these results indicate a role for nerve growth factor
acting via the TrkA receptor on ChAT and VAChT proteins in contextual
memory consolidation.
Key words:
neurotrophins; Pavlovian conditioning; neural plasticity; hippocampus; DNA oligonucleotides; choline acetyltransferase; vesicular
acetylcholine transporter
Copyright © 2001 Society for Neuroscience 0270-6474/01/2131047-09$05.00/0