The spindle neurons are present in the cingulate cortex of chimpanzee fetus

We report the existence of the spindle neurons in layer Vb of the anterior cingulate cortex (Brodman's area 24b) in a chimpanzee fetus (embryonic day 224), which was stillborn. About 5.3% of neuronal cells in layer Vb were the spindle neurons at this stage. The width of the spindle neurons was 10-15 microm. In layer V of the prefrontal cortex (Brodman's area 46) in the chimpanzee fetus, and in layer Vb of the cingulate cortex in adult macaque monkeys, no spindle neurons were observed. The immunoreactivity against brain-derived neurotrophic factor (BDNF) was detected only in the pyramidal neurons at this stage. These findings suggest that the existence of the spindle neurons in layer Vb of the anterior cingulate cortex and the presence of BDNF in the pyramidal neurons are intrinsically characterized during the embryonic stage of the chimpanzee.