Naturally occurring neuron death during postnatal development of the gerbil ventral cochlear nucleus begins at the onset of hearing.

Postnatal development of the gerbil ventral cochlear nucleus (VCN) was studied quantitatively under the light microscope in Nissl-stained serial sections at postnatal day 0 (P0), P5, P7, P10, P12, P15, and P140. VCN boundaries were unambiguous at all ages, and nucleus volume was calculated planimetrically for all groups. Measurements of neuron soma cross-sectional area and number were made in all groups except P0. Both VCN volume and soma area doubled between P5 and P10. Although somatic growth did not continue beyond P10, VCN volume increased a further 57% between P15 and P140. Neuron number did not change significantly between P5 and P10, averaging approximately 36,000 neurons. Between P10 and P12, neuron number decreased significantly by 22%, with no further change thereafter. Our data show that, following significant postnatal growth in the gerbil VCN, a brief period of naturally occurring neuron death begins at the onset of hearing.