title: Adaptive morphological changes of neocortical interneurons in response to enlarged and more complex pyramidal cells in p21H-Ras(Val12) transgenic mice.
abstract: Morphological features of interneuronal adaptation to an altered, more complex neuronal architecture have been investigated in p21H-Ras(Val12) transgenic mice. This transgenic strain serves as a model for studying the morphogenetic role of the G-protein p21Ras on cortical principal neurons. We have recently demonstrated that postmitotic expression of constitutively active p21H-Ras(Val12) in the neocortical pyramidal cell population results in increased size and dendritic complexity of the affected neurons, leading to an enlarged cortical volume. Interneurons do not express the transgene and are therefore excluded from direct, intrinsic p21H-Ras(Val12) effects. In the present study, immunolabelling of gamma-amino-butyric-acid (GABA), and of the calcium-binding proteins parvalbumin, calbindin and calretinin revealed that in the transgenic mice local circuit neurons are not increased in either somal size or number and their main morphological characteristics are preserved. However, the dendritic arbour of interneurons was found to be extended, at least in the vertical dimension, to follow the cortical expansion. Immunostaining for the vesicular GABA transporter revealed a denser inhibitory innervation of p21H-Ras(Val12)-expressing pyramidal cell perikarya than in those of wild-type animals, while the overall density of inhibitory axon terminals within the cortex was decreased in the transgenic animals as a consequence of cortical expansion. The findings of the present study demonstrate the morphogenetic capacity of interneurons for adapting to morphological alterations of principal neurons in the cerebral cortex.
authors.affiliation: Department of Neuroanatomy, Paul Flechsig Institute for Brain Research, University of Leipzig, D-04109 Leipzig, Germany. dralpar@gmx.net
authors.forename: Alán
authors.initials: A
authors.lastname: Alpár
authors.forename: Gudrun
authors.initials: G
authors.lastname: Seeger
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Härtig
authors.forename: Thomas
authors.initials: T
authors.lastname: Arendt
authors.forename: Ulrich
authors.initials: U
authors.lastname: Gärtner
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000818:Animals; D048429:Cell Size / Q000235:genetics; D007395:Interneurons / Q000166:cytology* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D019579:Neocortex / Q000166:cytology* / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*; D017966:Pyramidal Cells / Q000166:cytology* / Q000378:metabolism
chemical_list: D016283:Proto-Oncogene Proteins p21(ras)