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Exuberant thalamocortical axon arborization in cortex‐specific NMDAR1 knockout mice
Author(s) -
Lee LiJen,
Iwasato Takuji,
Itohara Shigeyoshi,
Erzurumlu Reha S.
Publication year - 2005
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.20481
Subject(s) - barrel cortex , neuroscience , somatosensory system , biology , postsynaptic potential , axon , nmda receptor , knockout mouse , cortex (anatomy) , cerebral cortex , axon terminal , thalamus , anatomy , receptor , biochemistry
Development of whisker‐specific neural patterns in the rodent somatosensory system requires NMDA receptor (NMDAR)‐mediated activity. In cortex‐specific NR1 knockout (Cx NR1 KO) mice, while thalamocortical afferents (TCAs) develop rudimentary whisker‐specific patterns in the primary somatosensory (barrel) cortex, layer IV cells do not develop barrels or orient their dendrites towards TCAs. To determine the role of postsynaptic NMDARs in presynaptic afferent development and patterning in the barrel cortex, we examined the single TCA arbors in Cx NR1 KO mice between postnatal days (P) 1–7. Sparsely branched TCAs invade the cortical plate on P1 in Cx NR1 KO mice as in control mice. In control animals, TCAs progressively elaborate patchy terminals, mostly restricted to layer IV. In Cx NR1 KO mice, TCAs develop far more extensive arbors between P3–7. Their lateral extent is twice that of controls from P3 onwards. By P7, Cx NR1 KO TCAs have significantly fewer branch points and terminal endings in layers IV and VI but more in layers II/III and V than control mouse TCAs. Within expansive terminal arbors, Cx NR1 KO TCAs develop focal terminal densities in layer IV, corresponding to the rudimentary whisker‐specific patches. Given that thalamic NMDARs are spared in Cx NR1 KO mice, the present results show that postsynaptic NMDARs play an important role in refinement of presynaptic afferent arbors and whisker‐specific patterning in the developing barrel cortex. J. Comp. Neurol. 485:280–292, 2005. © 2005 Wiley‐Liss, Inc.