TrkA expression in the CNS: evidence for the existence of several novel NGF-responsive CNS neurons.
NGF acts as a neurotrophic factor by binding and activating its receptor on certain neuronal populations in the CNS and PNS. TrkA is a receptor for NGF. Recent findings in vitro indicate that this NGF-activated receptor tyrosine kinase transduces the NGF signal. To further define NGF actions in the CNS, we examined trkA expression in the adult rat brain. We found that trkA mRNA and immunoreactivity (IR) coincided in specific, defined neuronal populations in the forebrain and brainstem. In addition to cholinergic neurons in the basal forebrain and neostriatum, trkA expression was found in noncholinergic neurons in (1) the paraventricular anterior and reuniens thalamic nuclei, (2) the rostral and intermediate subnuclei of the interpeduncular nucleus (IPN), (3) scattered neurons in the ventrolateral and paramedian medulla, (4) the prepositus hypoglossal nucleus, and (5) the area postrema. NGF responsiveness was demonstrated for each of these populations. In contrast to trkA, p75NGFR was found only in a minority of NGF-responsive populations. Our data provide further evidence that expression of trkA marks NGF-responsive CNS neurons and suggests novel roles for NGF in the brain.
Holtzman
D M
DM
Department of Neurology, University of California at San Francisco 94143.
Kilbridge
J
J
Li
Y
Y
Cunningham
E T
ET
Lenn
N J
NJ
Clary
D O
DO
Reichardt
L F
LF
Mobley
W C
WC
D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D001933:Brain Stem / Q000166:cytology / Q000378:metabolism; D005260:Female; D006651:Histocytochemistry; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D009414:Nerve Growth Factors / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D016548:Prosencephalon / Q000166:cytology / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D020917:Receptor, trkA; D017475:Receptors, Nerve Growth Factor / Q000235:genetics / Q000378:metabolism*; D014018:Tissue Distribution
D009414:Nerve Growth Factors; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D017475:Receptors, Nerve Growth Factor; D020794:Receptor Protein-Tyrosine Kinases; D020917:Receptor, trkA