title: Feeding-modulatory effects of mu-opioids in the medial prefrontal cortex: a review of recent findings and comparison to opioid actions in the nucleus accumbens.
abstract: Whereas reward-modulatory opioid actions have been intensively studied in subcortical sites such as the nucleus accumbens (Acb), the role of cortical opioid transmission has received comparatively little attention.
  
  
  
  The objective of this study is to describe recent findings on the motivational actions of opioids in the prefrontal cortex (PFC), emphasizing studies of food motivation and ingestion. PFC-based opioid effects will be compared/contrasted to those elicited from the Acb, to glean possible common functional principles. Finally, the motivational effects of opioids will be placed within a network context involving the PFC, Acb, and hypothalamus.
  
  
  
  Mu-opioid receptor (μ-OR) stimulation in both the Acb and PFC induces eating and enhances food-seeking instrumental behaviors; μ-OR signaling also enhances taste reactivity within a highly circumscribed zone of medial Acb shell. In both the Acb and PFC, opioid-sensitive zones are aligned topographically with the sectors that project to feeding-modulatory zones of the hypothalamus and intact glutamate transmission in the lateral/perifornical (LH-PeF) hypothalamic areas is required for both Acb- and PFC-driven feeding. Conversely, opioid-mediated feeding responses elicited from the PFC are negatively modulated by AMPA signaling in the Acb shell.
  
  
  
  Opioid signaling in the PFC engages functionally opposed PFC➔hypothalamus and PFC➔Acb circuits, which, respectively, drive and limit non-homeostatic feeding, producing a disorganized and "fragmented" pattern of impulsive food-seeking behaviors and hyperactivity. In addition, opioids act directly in the Acb to facilitate food motivation and taste hedonics. Further study of this cortico-striato-hypothalamic circuit, and incorporation of additional opioid-responsive telencephalic structures, could yield insights with translational relevance for eating disorders and obesity.
authors.affiliation: Department of Cellular and Molecular Pharmacology, Rosalind Franklin University of Medicine & Science, 3333 Green Bay Rd., North Chicago, IL, 60064, USA.
authors.forename: Ryan A
authors.initials: RA
authors.lastname: Selleck
authors.affiliation: Department of Psychiatry, University of Wisconsin-Madison School of Medicine and Public Health, 6001 Research Park Blvd., Madison, WI, 53719, USA. babaldo@wisc.edu.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Baldo
mesh_terms: D000701:Analgesics, Opioid / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D004435:Eating / Q000187:drug effects / Q000502:physiology; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism; D007175:Impulsive Behavior / Q000187:drug effects / Q000502:physiology; D009042:Motivation / Q000187:drug effects / Q000502:physiology; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism*; D017397:Prefrontal Cortex / Q000187:drug effects / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000378:metabolism*
chemical_list: D000701:Analgesics, Opioid; D017450:Receptors, Opioid, mu
keywords: ACCUMBENS; Dopamine; Feeding; Hypothalamus; Motivation; Opiate; Opioid; Prefrontal cortex