NTRK2 and neurodegenerative disease: One limitation of our study is that, in TrkbPenk-KO mice, Ntrk2 has also been deleted from striatal enkephalinergic neurons, an aspect that allowed for an investigation of the role of dysfunctional BDNF–TrkB signalling in Huntington’s disease (HD), a neurodegenerative disease characterised by striatal dysfunction [59], in a previous study [17].