Behaviors associated with food seeking, recognition, and ingestion can be categorized as appetitive versus consummatory, according to traditional analyses of animal behavior (Kupfermann, Carfilzomib 1974a; Lorenz, 1950). The first category corresponds to exploratory behavior that is subject to environmental influence and that may displays variability. The consummatory category

refers to the release and execution of innate behavioral sequences and its display is more or less invariant. Single neuropeptides (like neuropeptide Y [NPY]) contribute to both appetitive and consummatory feeding behaviors in mammals (Dailey and Bartness, 2009), and their roles in the fundamental neuronal circuits underlying feeding behaviors have been intensively studied. For example, detailed models are now emerging the explain how peptidergic neurons in the arcuate nucleus that secrete Agouti-related peptide (AgRP), GABA, and NPY promote feeding by inhibiting other neurons of the parabrachial, arcuate, and paraventricular nuclei of the hypothalamus (Aponte et al., 2011; Atasoy et al., 2012; Wu et al., 2009). That action depends on GABA and NPY

more than AgRP, and is age-dependent and subject to hormonal modulation (Yang et al., 2011) (Luquet et al., 2005). To complement such advancing mammalian studies, invertebrate model systems offer sophisticated PD0325901 concentration genetic manipulation and/or favorable cellular resolution: these features can help address the basis for the profound effects peptide modulators have on feeding behavior. In this section, we overview several different invertebrate studies (in insects, in Caenorhabditis elegans, in Aplysia) to illustrate potential cellular mechanisms of how peptide modulation may contribute to shape both appetitive and consummatory feeding behaviors. The motivational state profoundly influences the specific responses animals display in response to identical, food-associated stimuli (Kupfermann, 1974b). In Drosophila, neuropeptides implicated

in regulating feeding-associated behaviors include the NPY homolog, NPF ( Krashes et al., 2009; Wu et al., 2005a, 2005b), which, like NPY, appears to be specifically dedicated to modulation of circuits involved only in metabolism, stress, and energy homeostasis ( Nässel and Wegener, 2011). Other feeding-associated peptides include hugin ( Melcher and Pankratz, 2005), leukokinin ( Al-Anzi et al., 2010), and allatostatin A ( Hergarden et al., 2012). For example, starvation increases food-searching behavior by the fly and increases physiological responsiveness in an identified olfactory glomerulus called DM1. DM1 normally responds to cider vinegar and its state-dependent responsiveness is increased due to the actions of a neuropeptide called small NPF (sNPF). sNPF is genetically distinct from NPF, is found at all levels of the neuraxis, and is probably involved in many diverse modulatory functions ( Nässel and Wegener, 2011).