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[P214]: The bHLH transcription factor Olig3 marks the dorsal neuroepithelium of the hindbrain and is pivotal for the development of hindbrain nuclei
Author(s) -
Reuter K.,
Wende H.,
Sieber M.,
Mueller T.,
Oeczelik C.,
Birchmeier C.
Publication year - 2006
Publication title -
international journal of developmental neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.761
H-Index - 88
eISSN - 1873-474X
pISSN - 0736-5748
DOI - 10.1016/j.ijdevneu.2006.09.274
Subject(s) - hindbrain , center (category theory) , dorsum , biology , neuroscience , anatomy , chemistry , central nervous system , crystallography
Although the NMDA receptor is known to play a crucial role in activity-dependent remodeling of synaptic connections in the fetal brain, its contribution to the electrical activity of fetal brain neurons has not been determined. We therefore performed optical recordings using voltageand Ca-sensitive fluorescent dyes (RH795 and Fura-2/AM, respectively) to analyze synaptic transmission in the superior colliculus (SC) in fetal rats, which were still connected with the dams by the umbilical cord. Fetuses were used at embryonic day 22. Pregnant rats were anesthetized with urethane (1.2–1.4 g/kg, i.p.). The head of the fetus was fixed to a conventional stereotaxic apparatus according to the method that we have previously devised. After a stimulating bipolar electrode was inserted in the SC, the fluorescent dye was loaded to the surface of the SC. The neuronal responses and changes in [Ca]i of the SC to focal electrical stimulation of the SC were recorded as fractional changes in fluorescence intensity using optical recording systems (ARGUS-50 for the voltage recordings and HiSCA for Ca measurements, Hamamatsu Photonics). Excitatory and inhibitory responses were evoked by focal SC stimulation. The excitatory synaptic responses were composed of early and late components. The early component was mediated by both non-NMDA and NMDA receptors, whereas the late component occurred mainly via NMDA receptors. Train pulse stimulation at higher currents was required for induction of the inhibition, which was antagonized by bicuculline, and blocking of the GABA-mediated inhibition by bicuculline uncovered masked excitatory synaptic responses. Focal SC stimulation induced increases in [Ca]i that were mediated mainly by NMDA receptors. GABA antagonists augmented SC-induced increases in [Ca]i. These results indicate that in the fetal SC, excitatory and inhibitory synaptic transmissions occur before birth and that the NMDA receptor is a major contributor to excitatory synaptic transmission and increased [Ca]i.