Effects of food restriction on expression of place conditioning and biochemical correlates in rat nucleus accumbens.
| Publication Type | Academic Article |
| Authors | Jung C, Rabinowitsch A, Lee W, Zheng D, de Vaca S, Carr K |
| Journal | Psychopharmacology (Berl) |
| Volume | 233 |
| Issue | 17 |
| Pagination | 3161-72 |
| Date Published | 07/04/2016 |
| ISSN | 1432-2072 |
| Keywords | Conditioning, Psychological, Extinction, Psychological, Food Deprivation, Morphine, Narcotics, Nucleus Accumbens, Receptors, AMPA |
| Abstract | RATIONALE: When ad libitum-fed rats undergo cocaine place preference conditioning (CPP) but are switched to food restriction for testing, CPP becomes resistant to extinction and correlates with phosphorylation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor GluA1 at Ser845 in nucleus accumbens (NAc) core. OBJECTIVES: This study tested whether food restriction increases persistence of morphine CPP and conditioned place aversions (CPA) induced by LiCl and naloxone-precipitated morphine withdrawal. MATERIALS AND METHODS: Ad libitum-fed rats were conditioned with morphine (6.0 mg/kg, i.p.), LiCl (50.0/75.0 mg/kg, i.p.), or naloxone (1.0 mg/kg, s.c.) 22 h post-morphine (20.0 mg/kg, s.c.). Half of the subjects were then switched to food restriction. Daily testing resumed 3 weeks later, and brains were harvested when one diet group met extinction criterion. Western analyses probed for pSer845-GluA1, pERK1, and pERK2 in NAc. RESULTS: Food restriction increased persistence of morphine CPP and preference scores correlated with pSer845-GluA1 in NAc core and shell. LiCl CPA was curtailed by food restriction, yet pSer845-GluA1 and pERK2 were elevated in NAc core of food-restricted rats. Food restriction increased persistence of naloxone CPA and elevated pSer845-GluA1 in NAc core and shell, and aversion scores were negatively correlated with pERK1 and pERK2 in NAc core. CONCLUSIONS: These results suggest that food restriction prolongs responsiveness to environmental contexts paired with subjective effects of both morphine and morphine withdrawal. A mechanistic scheme, attributing these effects to upregulation of pSer845-GluA1, but subject to override by CPA-specific, pERK2-mediated extinction learning, is explored to accommodate opposite effects of food restriction on LiCl and naloxone CPA. |
| DOI | 10.1007/s00213-016-4360-4 |
| PubMed ID | 27376947 |
| PubMed Central ID | PMC4982816 |