Do BDNF and NT-4/5 exert synergistic or occlusive effects on corticostriatal transmission in a male mouse model of Huntington's disease?

Brain-derived neurotrophic factor (BDNF) and neurotrophin-4/5 (NT-4/5) are trophic factors belonging to the neurotrophin family; in addition to their trophic role, both neurotrophins play an important role in modulating corticostriatal synaptic transmission. Failures in BDNF supply and mitochondrial dysfunction are among the factors involved in the striatal degeneration that occurs in Huntington's disease (HD). While the effects of BDNF have been widely studied in striatal degeneration, the role of NT-4/5 has been less addressed. NT-4/5 does not appear to exert effects similar to those of BDNF in HD. The physiological roles of these molecules in corticostriatal transmission have been evaluated separately, and we have demonstrated that sequential exposure to both neurotrophins results in different modulatory effects on corticostriatal transmission depending on the exposure order. In the present study, we evaluated the effects of BDNF followed by NT-4/5 or NT-4/5 followed by BDNF on corticostriatal synaptic transmission with field recordings in a male mouse model of HD produced by in vivo treatment with the mitochondrial toxin 3-nitropropionic acid. Here, we show that these neurotrophins elicit an antagonistic or synergistic effect that depends on the activation of the truncated isoform or the stimulation of the full-length isoform of the tropomyosin receptor kinase B (TrkB).