mice. Similarly, fifteen different neurofilament heavy polypeptide (NFH) phosphopeptides were found to be differentially expressed between groups. NFH is a known target of numerous protein kinases, and these phosphorylation events regulate the interaction between different neurofilament subunits and other cytoskeletal structures to provide stability to mature axons (Yuan et al. 2017). Although neurofilaments were previously thought to be axonal contaminants, accumulating evidence indicates neurofilaments are present in the synapse (Yuan & Nixon 2016), particularly the postsynaptic density where they have been shown to co-localize with the NR1 NMDA receptor subunit, the D1 dopamine receptor, and spinophilin (Baucum et al. 2010; Yuan et al. 2015; Ehlers et al. 1998; Hiday et al. 2017). Interestingly, chronic cocaine, morphine, nicotine, and alcohol administration reduces neurofilament concentrations in the ventral tegmental area suggesting changes to neurofilament integrity may be a shared drug-induced structural change in brain regions important for drug reward (Beitner-Johnson et al. 1992; Ortiz et al. 1995; Bunnemann et al. 2000).
