The Journal of Neuroscience, February 1, 2002, 22(3):912-919
Expression of the Nerve Growth Factor Receptors TrkA and
p75NTR in the Visual Cortex of the Rat: Development and
Regulation by the Cholinergic Input
Francesco Mattia
Rossi1,
Roberta
Sala1, and
Lamberto
Maffei1, 2
1 Scuola Normale Superiore, 56126 Pisa, Italy, and
2 Istituto di Neurofisiologia del Consiglio Nazionale delle
Ricerche, 56100 Pisa, Italy
Several lines of evidence have shown that nerve growth factor
(NGF), the progenitor of the neurotrophin family of growth factors, plays a fundamental role in the developmental plasticity of the rat
visual cortex. However, the expression of NGF receptors (NGFRs) TrkA
and p75NTR and the possible sites of NGF action in
the visual cortex remain to be elucidated so far. Using a highly
sensitive ECL immunoblot analysis, we have been able to show, in the
present study, that the TrkA protein is expressed in the rat visual
cortex and that it is developmentally upregulated during the critical
period for cortical plasticity. In contrast, the expression level of
the low-affinity NGF receptor p75NTR seems to remain
nearly constant throughout development. In the analysis of possible
pathways involved in the regulation of NGFR expression, we found that
neither blockade of the visual input nor NGF administration to the
visual cortex resulted in a modulation of NGFR levels of expression. On
the other hand, the selective destruction of cholinergic afferents to
the visual cortex caused a dramatic, but not complete, reduction of the
cortical NGFRs, which suggests that these receptors are located on
cholinergic terminals predominantly. At the functional level, we found
that, after the elimination of the cholinergic afferents to the visual cortex, the NGF-induced increase of both acetylcholine and glutamate release from cortical synaptosomes was strongly impaired. These results
indicate that the cholinergic input is an important mediator of visual
cortex responsiveness to NGF action.
Key words:
acetylcholine; glutamic acid; nerve growth factor; neurotransmitter release; p75NTR; synaptosomes; TrkA; visual cortex; Western blot
Copyright © 2002 Society for Neuroscience 0270-6474/02/223912-08$05.00/0
Previous Article | Next Article
