Expression of nerve growth factor and neurotrophin-3 mRNAs in hippocampal interneurons: morphological characterization, levels of expression, and colocalization of nerve growth factor and neurotrophin-3.
We have investigated the distribution and morphology of hippocampal interneurons that express the neurotrophins nerve growth factor (NGF) and neurotrophin-3 (NT-3) in the rat. For this study, we combined in situ hybridization for the detection of NGF and NT-3 mRNAs and immunocytochemistry against the calcium-binding proteins parvalbumin (PARV), calretinin (CALR), and calbindin (CALB). Whereas the majority of PARV+ interneurons expressed NGF mRNA, only subsets of CALR- and CALB-immunoreactive interneurons (23% and 24%, respectively) displayed NGF hybridization. Most CALB/NGF+ cells were located in the stratum oriens/alveus of the CA3-CA1 regions, suggesting that they may include the population of CALB+, hippocamposeptal, nonpyramidal neurons. Most of the nonspiny CALR/NGF+ neurons were located within or in the vicinity of the pyramidal layer and had faint CALR immunostaining and stellate, thin dendrites. Regarding the spiny CALR-immunoreactive cells, we found that most of these neurons in the hilus were NGF+, whereas only 59% of displayed NGF hybridization in the stratum lucidum of the CA3 region. A small subset of PARV- and CALR-immunoreactive cells expressed NT-3 mRNA (16% and 13%, respectively). NT-3 message was not found in the large basket cells of the dentate gyrus, whereas the distribution and morphology of CALR/NT-3+ cells were similar to those of nonspiny CALR/NGF+ cells. In fact, double in situ hybridization analysis confirmed that most NT-3+ neurons also expressed NGF mRNA, indicating coexpression of both neurotrophins in subpopulations of PARV+ and CALR+ neurons. Moreover, the level of NGF mRNA expression was higher in PARV+ neurons than in CALR- and CALB-immunoreactive interneurons, whereas NT-3 message was expressed similarly in PARV+ and CALR+ neurons. The present findings show a differential expression of NGF and NT-3 mRNAs in subsets of hippocampal interneurons and suggest that the expression of these transcripts depends on factors intrinsic to particular cell types.
Pascual
M
M
Department of Animal and Plant Cell Biology, Faculty of Biology, University of Barcelona, Spain.
Rocamora
N
N
Acsády
L
L
Freund
T F
TF
Soriano
E
E
D000818:Animals; D064026:Calbindins; D006624:Hippocampus / Q000737:chemistry* / Q000166:cytology; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007395:Interneurons / Q000737:chemistry*; D009414:Nerve Growth Factors / Q000235:genetics*; D009419:Nerve Tissue Proteins / Q000032:analysis; D009474:Neurons / Q000737:chemistry; D020933:Neurotrophin 3; D010320:Parvalbumins / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D064030:S100 Calcium Binding Protein G / Q000032:analysis
D064026:Calbindins; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D020933:Neurotrophin 3; D010320:Parvalbumins; D064030:S100 Calcium Binding Protein G