Glial cell line-derived neurotrophic factor in genetically defined fear-induced aggression

Glial cell line-derived neurotrophic factor (GDNF) plays an important role in maintenance of neuronal system throughout life. However, there is a lack of data on the involvement of GDNF in the regulation of different kinds of behavior. In this study, GDNF, its precursor (proGDNF) and GDNF mRNA levels were investigated in the brain of rats selectively bred for 85 generations for either high level or for the lack of affective aggressiveness toward human. It was found that GDNF mRNA level was decreased in the frontal cortex, increased in the raphe nuclei area of the midbrain of aggressive rats compared to tame animals and was not detected in the amygdala and hypothalamus. The level of proGDNF was reduced in the raphe nuclei area of the midbrain of highly aggressive rats and was not detected in the striatum, nucleus accumbens of investigated animals. Two forms of mature GDNF - monomer and dimer - were revealed. GDNF monomer level was increased in the raphe nuclei area, substantia nigra and amygdala of aggressive rats and it was not found in the frontal cortex and nucleus accumbens of investigated rats. Dimer GDNF level was found in all investigated brain structures. It was reduced in the hippocampus and increased in amygdala of highly aggressive rats. Thus, considerable structure-specific differences in GDNF expression between highly aggressive and nonaggressive rats were shown. The data suggested the implication of both mature GDNF monomer and dimer as well as proGDNF in the mechanism underlying genetically defined aggressiveness.