Stress, Neuropeptides, and Feeding Behavior: A Comparative Perspective

Abstract

Stress inhibits feeding behavior in all vertebrates. Data from mammals suggest an important role for hypothalamic neuropeptides, in particular the melanocortins and corticotropin-releasing hormone (CRH)-like peptides, in mediating stress-induced inhibition of feeding. The effects of CRH on food intake are evolutionarily ancient, as this peptide inhibits feeding in fishes, birds, and mammals. The effects of melanocortins on food intake have not been as extensively studied, but available evidence suggests that the anorexic role of neuronal melanocortins has been conserved. Although there is evidence that CRH and the melanocortins influence hypothalamic circuitry controlling food intake, these peptides may have a more primitive role in modulating visuomotor pathways involved in the recognition and acquisition of food. Stress rapidly reduces visually guided prey-catching behavior in toads, an effect that can be mimicked by administration of CRH, while corticosterone and isoproterenol are without effect. Melanocortins also reduce prey-oriented turning movements and, in addition, facilitate the acquisition of habituation to a moving prey item. The effects of these neuropeptides are rapid, occurring within 30 min after administration. Thus, changes in neuroendocrine status during stress may dramatically influence the efficacy with which visual stimuli release feeding behavior. By modulating visuomotor processing these neuropeptides may help animals make appropriate behavioral decisions during stress.

Profile of cortisol, glycaemia, and blood parameters of American Bullfrog tadpoles Lithobates catesbeianus exposed to density and hypoxia stressors

“…Glycaemia is one of the most used stress indicators of secondary physiological responses, where it increases in the presence of any stressor in order to meet the higher energy demand needed to escape or to confront an adverse situation (Heinrichs & Richard 1999, Richard et al 2002, Sapolsky et al 2000, Carr 2002, Crespi & Denver 2005 Although there are several studies about blood glucose levels on amphibians, these are not easily interpreted due to variations of factors such as feeding, life stage, and even collection methods (Herman 1992). In aquaculture, stocking density is an important factor influencing food ingestion and is species-specific.…”

The Endocrine Response to Stress - A Comparative View

“…Although there is evidence that CRH and the melanocortins influence hypothalamic circuitry controlling food intake, these peptides may have a more primitive role in modulating visuomotor pathways involved in the recognition and acquisition of food. (Carr, 2002). Stress rapidly reduces visually guided prey-catching behavior in toads, an effect that can be mimicked by administration of CRH, while corticosterone and isoproterenol are without effect.…”

Current research in amphibians: Studies integrating endocrinology, behavior, and neurobiology

“…No current research targets seasonal homing or migration, but a few studies have investigated the behavioral endocrinology of energetics as related to mate signaling (Marler and Ryan, 1996) and foraging (Carr, 2002;Crespi and Denver, 2004). The role of thyroxin in triggering metamorphosis and the subsequent reconfiguration of the endocrine system is well known (Burggren and Just, 1992), and there is a substantial body of work on the interaction of environmental stress, corticotrophin-releasing hormone, and thyroxin in adaptively regulating metamorphosis (Denver et al, 2002;Boorse and Denver, 2004), but behavioral correlates (other than sexual development) are not precisely understood.…”