International journal of developmental neuroscience : the official journal of the International Society for Developmental Neuroscience
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Int. J. Dev. Neurosci. · Nov 1996
Essential role of thyroid hormones in maturation of olfactory receptor neurons: an immunocytochemical study of number and cytoarchitecture of OMP-positive cells in developing rats.
Neurogenesis and proliferation of olfactory receptor neurons (ORNs) in the olfactory epithelium (OE) are reduced in postnatal hypothyroid rats and upregulated following restoration of thyroid function, leading to compensatory growth and restitution of these deficits [Paternostro M. A. and Meisami E. (1993). Dev. ⋯ Withdrawal of PTU resulted in marked restoration of these deficits so that, at 90 days, the total number of OMP(+) cells were only 20% less than 90-day-old controls. These results indicate that thyroid hormones are essential for maturation of single ORNs and accretion of new mature ORNs in the OE of suckling and post-weaning rat. Also, the process of maturation and the final number of mature ORNs show remarkable recovery from hypothyroid-induced growth retardation.
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Int. J. Dev. Neurosci. · Nov 1996
Regulation of c-Fos mRNA and fos protein expression in olfactory bulbs from unilaterally odor-deprived adult mice.
Odorant deprivation, produced by unilateral naris closure, profoundly reduces tyrosine hydroxylase (TH) expression within intrinsic olfactory bulb dopamine neurons. The TH gene contains an AP-1 site, which interacts with the product of the immediate early gene, c-fos. c-Fos exhibits activity dependent regulation in the CNS. The hypothesis that odorant stimulation and deprivation might modify c-fos expression in TH neurons was tested in adult CD-1 mice, subjected to unilateral naris closure. ⋯ In olfactory bulbs ipsilateral to naris closure, odor stimulation also induced c-fos mRNA expression in the mitral and granule cell layers and sparsely within limited periglomerular regions. Odor induced expression in mitral and granule cell layers may represent increased centrifugal activity acting on as yet unknown genes. These results suggest a correlation between c-fos mRNA expression and increased neuronal activity in the olfactory bulb which, in turn, acts to regulate TH expression in periglomerular neurons.