series of signaling pathways critical to cell life (Rego and Oliveira 2003; Rimessi et al. 2008; Szabadkai and Duchen 2008). Recent work also has demonstrated that these pathways, including the protein kinase A (PKA) and C (PKC) signaling cascades, are important regulators of mitochondrial energy production. In particular, they are able to act on the electron transport system through tyrosine phosphorylation (Huttemann et al. 2007; Salvi et al. 2005). Directly or indirectly, nicotine can trigger various intracellular signaling pathways, including PKC and MAPK, in neurons of different brain regions (Konu et al. 2001; Li et al. 2004; Quik 2004). Thus, the regulation of the intracellular signaling pathways in response to nicotine may lead to regulation of the electron transport system and, eventually, modulation of mitochondrial function.
