Morphometric analysis and retrograde tracing studies showed that no injured neurons smaller than 600 microm2 were immunoreactive for brain - derived neurotrophic factor , whereas the majority of large injured neurons were immunoreactive in the ipsilateral dorsal root ganglia seven days postlesion .
These studies indicate that sciatic nerve injury results in a differential regulation of brain - derived neurotrophic factor in different subpopulations of sensory neurons in the dorsal root ganglia .
The percentage of neurons immunoreactive for brain - derived neurotrophic factor in the ipsilateral dorsal root ganglia was significantly increased as early as 24 h after the nerve lesion and the increase lasted for at least two weeks .
Both neurons and satellite cells in the lesioned dorsal root ganglia synthesized brain - derived neurotrophic factor messenger RNA after the nerve lesion .
The level of brain - derived neurotrophic factor messenger RNA was also significantly increased in the ipsibut not contralateral dorsal root ganglia .