Acquiring the necessary balance of nutrients in one’s diet is a compelling problem faced by many animals including humans. For the macronutrient protein, this process is particularly pertinent as essential amino acids cannot be stored so must be constantly sourced through dietary choices. Thus, behavioural and physiological mechanisms likely exist to help compensate for any deficiency. Accordingly, we and others have shown that animals fed a low-protein diet develop a strong preference for protein over carbohydrate. This preference develops rapidly and is also associated with increased motivation for protein in an operant-responding paradigm. To explore the neural basis of this shift in behaviour we have been using a combination of calcium imaging, voltammetry, and activity-dependent “trapping” of neural populations in rodents. Using fibre photometry and voltammetry, we have shown that mesolimbic circuitry is modulated by the state of protein restriction with activity in ventral tegmental area and forebrain dopamine release elevated when animals are in need. In addition, with single cell multiphoton microscopy we have shown that an important projection to the VTA – vGAT neurons in lateral hypothalamus – are similarly modulated by the state of protein restriction. Furthermore, we are using transgenic FosTRAP mice to identify how the state of protein restriction alters whole-brain patterns of neural activity evoked by consumption of protein and infusion of protein directly into the stomach.