AI Article Synopsis

  • The study investigated the timing of neuron generation in the lateral superior olive (LSO) of rats that project to different inferior colliculus (IC) sides.
  • Rat fetuses were exposed to a marker to label neuron development, revealing that neurons projecting to the contralateral IC are produced earlier than those projecting to the ipsilateral IC.
  • Findings show that LSO neurons are generated between embryonic days E12-E16, with no organized spatial arrangement between the early- and late-generated neurons.

Article Abstract

The present study examined in the lateral superior olive (LSO) of the rat whether LSO neurons projecting to the ipsilateral inferior colliculus (IC) might be generated later than those projecting to the contralateral IC. Rat fetuses were exposed in utero to 5-bromodeoxyuridine (BrdU), a thymidine analogue, to label neurons proliferating at different embryonic stages from day E11 through to E20. Upon reaching adulthood, the rats were given unilateral injections of fluoro-gold (FG), a retrograde fluorescent tracer, into the IC. Subsequently, the tissue sections of the brains obtained from the rats were immunostained for BrdU to simultaneously detect neurons that were BrdU-positive and/or FG-positive. BrdU-positive LSO neurons were found in the rats which had been exposed to BrdU during E12-E16. In E12 and E13 BrdU-exposure cases, the vast majority of doubled-labeled (BrdU-positive and FG-positive) neurons were seen on the contralateral side to the FG injection. In E14, E15 and E16 BrdU-exposure cases, in contrast, all double-labeled neurons were found on the ipsilateral side to the FG injection. The distribution of these double-labeled neurons within the nucleus was diffuse in all the BrdU-exposure cases. Thus, the results indicate that LSO neurons are generated during E12-E16, that the crossed projection neurons are generated 1-4 days earlier than the uncrossed projection neurons, and that no topographical relationships exist between the early- and the late-generated populations of the LSO neurons.

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http://dx.doi.org/10.1016/0165-3806(96)00081-8DOI Listing

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