Establishing digital stereology protocols to determine potential neurogenic effects of novel α6 neuronal nicotinic agonists in subgranular and subventricular neurogenic niches
Syposs, Chauncey R., IV
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In the past two decades adult neurogenesis (AN) has become a robust field of neuroscience. The goal of many scientists is to identify pharmacological agents that affect the proliferation, migration, and differentiation of neural stem cells (NSCs) in order to replace neurons lost due to developmental and degenerative neuropathology. One such class of compounds is neuronal nicotinic agonists (NNAs). Preliminary evidence suggests that certain sub-types of NNR agonists (α7, α4β2) significantly alter the proliferation of neuronal stem/progenitor cells and differentiation of neurons in mouse models; however, agonist of all receptor sub-types has not been extensively studied as of yet. We sought to determine whether α6 NNAs might affect AN in the dentate gyrus (DG) and cornu ammonis (CA) of the anterior hippocampus (aHI) in the standard C57BL/6J mouse by systematic uniform random sampling and unbiased stereological estimation following bromodeoxy-uridine (BrDU) labeling and treatment by one of two α6 NNAs. In addition I have initiated stereological analyses of bromodeoxy-uridine (BrdU) labeling in other regions of the brain: the Sub-Ventricular zone (SVZ) of the lateral ventricle (LV), the anterior cingulate cortex (ACC), and the substantia nigra pars compacta (SNpC). My study demonstrated significant increases in BrdU+ cell number in the dentate gyrus after administration of α6 NNAs (n=4; p= 0.053 LSD, p= 0.004 LSD, RB ANOVA) with decreased Ki67+ cell number, indicating a change from proliferation to a differentiation state. Preliminary results in other locations demonstrated no significant changes in BRDU+ were seen in the cornu ammonis (CA) of the HI, however no significant results were demonstrated due to low sample size. Co-immunohistochemical staining for BRDU and ontological markers of neuronal phenotype demonstrated BrDU/NeuN and BrDU/Calretinin co-localization in dental gyrus, demonstrating the adoption of neuronal lineage by new cells. We could not detect any colocalization between BrDU/GFAP in the hippocampus. These data suggest that α6 NNAs increase the rate of differentiation of neuronal stem cells in the SGZ of the HI. Preliminary counts suggest no effect in anterior cingulate cortex (ACC), or the substantia nigra pars compacta (SNpC).