title: Thyroid hormones affect neurogenesis in the dentate gyrus of adult rat.
abstract: Thyroid hormones play a crucial role in new neuron production and maturation during brain development. However, the knowledge about the involvement of these hormones on adult neurogenesis is still incomplete. Hippocampus is an anatomical region where neurogenesis occurs throughout adulthood and where high levels of thyroid hormone receptors have been found. In this work the possible involvement of thyroid hormones in the regulation of adult neurogenesis in the granule cell layer of rat hippocampus dentate gyrus was investigated using an experimental model of adult-onset pharmacologically-induced hypothyroidism. Neurogenesis was assessed by means of the thymidine analogue 5-bromo-2'-deoxyuridine 24 h and 30 days after its last administration in order to study neural precursor proliferation and newborn cell survival, respectively. Mitotic activity of the neural precursors was not affected by thyroid hormone deficiency; on the contrary, newborn cell survival dramatically decreased under these conditions when compared with controls, leading to a lower number of immature neurons being added to the granule cell layer. Moreover, in conditions of hypothyroidism, new neurons exhibit a delay in neuronal differentiation showing a prolonged expression of the neuritogenesis-associated immature neuron marker TUC-4 and a very immature morphology. Finally, the total number and size of granule cells, and granule cell layer volume decreased in hypothyroid rats. These results suggest that thyroid hormones play a role in regulating new neuron production during adult life in dentate gyrus of rat hippocampus.
authors.affiliation: Istituto di Scienze Fisiologiche, Università di Urbino Carlo Bo, Italia. p.ambrogini@uniurb.it
authors.forename: Patrizia
authors.initials: P
authors.lastname: Ambrogini
authors.forename: Riccardo
authors.initials: R
authors.lastname: Cuppini
authors.forename: Paola
authors.initials: P
authors.lastname: Ferri
authors.forename: Cecilia
authors.initials: C
authors.lastname: Mancini
authors.forename: Sandra
authors.initials: S
authors.lastname: Ciaroni
authors.forename: Adriana
authors.initials: A
authors.lastname: Voci
authors.forename: Ezio
authors.initials: E
authors.lastname: Gerdoni
authors.forename: Gabriella
authors.initials: G
authors.lastname: Gallo
mesh_terms: D000818:Animals; D017209:Apoptosis; D002454:Cell Differentiation; D002455:Cell Division; D002470:Cell Survival; D018891:Dentate Gyrus / Q000166:cytology*; D007037:Hypothyroidism / Q000097:blood / Q000139:chemically induced; D020287:In Situ Nick-End Labeling; D009420:Nervous System / Q000254:growth & development*; D009474:Neurons / Q000166:cytology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013234:Stem Cells / Q000166:cytology; D013963:Thyroid Hormones / Q000502:physiology*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D013963:Thyroid Hormones; D014284:Triiodothyronine; D013974:Thyroxine