Recent studies show that the non-opioid peptides, galanin (GAL) and orexin (OX), are similar to the opioid enkephalin (ENK) in being stimulated by dietary fat and also in enhancing the consumption of a high-fat diet (HFD). This suggests that, when an HFD is provided, these non-opioids may stimulate the opioid system to promote excess consumption of this diet. Using single- and double-labeling immunohistochemistry, the present study sought to identify possible neuroanatomical substrates for this close relationship. Focusing on the hypothalamic paraventricular nucleus (PVN), and particularly its anterior (aPVN), middle (mPVN) and posterior (pPVN) parts, the experiments examined whether GAL itself or the receptors for GAL and OX are stimulated by an HFD in the same areas and possibly the same neurons as ENK. Compared to animals fed a standard chow diet, rats consuming an HFD exhibited an increased density of medial parvocellular neurons immunoreactive (IR) for GAL in the mPVN and aPVN and for ENK in the mPVN and pPVN, distinguishing the mPVN as an area where both peptides were affected. While showing little evidence for GAL and ENK colocalization with a chow diet, double-labeling studies in HFD-fed rats revealed significant colocalization specifically in medial parvocellular neurons of the mPVN. Immediately posterior to this site, further analyses revealed a similar relationship between the OX 2 receptor (OX2R) and ENK in HFD-treated animals. While increasing the density of neurons immunoreactive for OX2R as well as for the GAL 1 receptor but not OX 1 receptor, HFD consumption increased the colocalization only of OX2R and ENK, specifically in the medial parvocellular neurons of the pPVN. These changes in HFD-fed rats, showing GAL and OX2R to colocalize with ENK exclusively in neurons of the medial parvocellular mPVN and pPVN, respectively, suggest possible neural substrates through which the non-opioid peptides may functionally interact with ENK when exposed to an HFD. Published by Elsevier Ltd on behalf of IBRO.
GALANIN AND THE OREXIN 2 RECEPTOR AS POSSIBLE REGULATORS OF ENKEPHALIN IN THE PARAVENTRICULAR NUCLEUS OF THE HYPOTHALAMUS: RELATION TO DIETARY FAT
Creators
J. R. Barson - Rockefeller University
G. -Q. Chang - Rockefeller University
K. Poon - Rockefeller University
I. Morganstern - Rockefeller University
S. F. Leibowitz - Rockefeller University
Publication Details
Neuroscience, v 193, pp 10-20
Publisher
Elsevier
Number of pages
11
Grant note
DA21518 / USPHS; United States Department of Health & Human Services; United States Public Health Service
R01DA021518 / NATIONAL INSTITUTE ON DRUG ABUSE; United States Department of Health & Human Services; National Institutes of Health (NIH) - USA; NIH National Institute on Drug Abuse (NIDA); European Commission
Resource Type
Journal article
Language
English
Academic Unit
Neurobiology and Anatomy; College of Medicine; Drexel University
Web of Science ID
WOS:000295189200002
Scopus ID
2-s2.0-80052451399
Other Identifier
991020112315304721
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