A fundamental aspect of coping in a diverse environment is to switch between motivational processes that drive appetitive approach responses, and those that promote avoidance (Alcaro and Panksepp, 2011; Korte et al., 2005). CRF is a prototypical neuropeptide that predominantly promotes withdrawal and attenuates appetitive behaviors, while NPY has the opposite profile. The interrelationship of these two prototypical neuropeptides can be conceptualized in a relatively straightforward manner as mediators of these opponent processes, and key elements of the neurocircuitry mediating their interactions, such as the amygdala complex, have been recognized for some time (Heilig et al., 1994). The urocortins, neurokinins, N/OFQ, and NPS have activity profiles that in part fall into these prototypical categories, but also differ from them in being more complex. Here, we will review key findings on each of the individual systems, discuss their similarities and differences, attempt to integrate their interrelationship and the anatomical structures through which they may interact, and identify knowledge gaps that need to be filled.
