Chemical identification of nestin-immunoreactive neurons in the rat basal forebrain: a re-examination

This study explores recently identified neurons that express the protein nestin in the medial septum-diagonal band of Broca (MS-DBB) of adult rats and humans. These nestin positive neurons from MS-DBB are known to project to the hippocampus and frontal cortex of the brain. However, their chemical identification has not been fully elucidated. In this study, we further investigated the chemical identity of the nestin-immunoreactive (ir) neurons in rats using double immunofluorescence labeling and single cell reverse transcription polymerase chain reaction (RT-PCR) techniques. The results of double labeling showed that all nestin-ir neurons exhibited choline acetyltransferase (ChAT) immunoreactivity in the MS-DBB of the basal forebrain. Conversely, only about 43% of the ChAT-ir neurons showed nestin immunoreactivity. In addition, a vast majority of the nestin-ir neurons (95%) were nerve growth factor receptor (NGFR) positive. The nestin-ir neurons were highly distributed in the rostral and intermediated regions of the MS-DBB. Single cell RT-PCR results showed that 90% of the nestin mRNA expressed neurons displayed ChAT mRNA expression as well, but neither the mRNA of the proteins glutamic acid decarboxylases 67 (GAD67) nor vesicular glutamate transporters (VGLUTs). These results provide the first evidence that nestin-ir neurons in the basal forebrain are a subpopulation of the classic cholinergic neurons. With high NGFR proteins activated in the nestin-ir neurons, we propose that the presence of nestin in the cholinergic neurons might be related to the survival and plasticity of the cholinergic neurons.