Tyrosine kinase B (TrkB) levels in the adult guinea pig cochlear nucleus (CN) were determined from Western blots for up to 60 days after unilateral cochlear ablation (UCA). Compared to TrkB levels on the intact side, those on the lesioned side were elevated in the anteroventral CN (AVCN) at 7 and 60 days and in the posteroventral CN (PVCN) at 30 days. TrkB levels were depressed in the AVCN and the dorsal CN (DCN) at 30 days. Elevations in the AVCN on the lesioned side at 7 days coincided with a period of synaptogenesis. Other changes were temporally related to up- or downregulations of transmitter release and synaptic receptor activities that were evident after UCA. The findings suggest that changes in signaling through TrkB may contribute to the plasticities in the CN that were evident after UCA.