GAP43 and Tinnitus: Other studies demonstrated increased cholinergic signalling in the VCN of hamsters (Jin et al., 2006), and elevated expression of GAP43 – a marker for plasticity – in the rat VCN (Michler & Illing, 2002; Kraus & Illing, 2004) following acoustic over-exposure, and that this could be linked to behavioural evidence of tinnitus (Kraus et al., 2011).