title: Nucleus accumbens injections of the mGluR2/3 agonist LY379268 increase cue-induced sucrose seeking following adult, but not adolescent sucrose self-administration.
abstract: Adolescence is often portrayed as a period of enhanced sensitivity to reward, with long-lasting neurobiological changes upon reward exposure. However, we previously found that time-dependent increases in cue-induced sucrose seeking were more pronounced in rats trained to self-administer sucrose as adults than as adolescents. In addition, adult, but not adolescent sucrose self-administration led to a decreased α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/N-Methyl-D-aspartate (AMPA/NMDA) ratio in the nucleus accumbens core, suggesting that long-lasting changes in glutamatergic transmission may affect adult processing of natural rewards. Here we tested whether altering glutamatergic transmission in the nucleus accumbens core via local injection of an mGluR2/3 agonist and antagonist affects cue-induced sucrose seeking following abstinence and whether this is different in the two age groups. Rats began oral sucrose self-administration training (10 days) on postnatal day (P) 35 (adolescents) or P70 (adults). Following 21 days of abstinence, rats received microinjections of the mGluR2/3 agonist LY379268 (0.3 or 1.0 μg/side) or vehicle into the nucleus accumbens core, and 15 min later cue-induced sucrose seeking was assessed. An additional group of rats trained as adults received nucleus accumbens core microinjections of the mGluR2/3 antagonist (RS)-α-Methyl-4-phosphonophenylglycine (MPPG) (0.12 or 0.5 μg/side). Confirming our previous results, adult rats earned more sucrose reinforcers, while sucrose intake per body weight was similar across ages. On abstinence day 22, local injection of the mGluR2/3 agonist LY379268 increased cue-induced sucrose seeking only in adult rats, and had no effect in adolescents. Local injections of the mGluR2/3 antagonist MPPG had no effect on sucrose seeking in adult rats. These data suggest an important developmental difference in the neural substrates of natural reward, specifically a difference in glutamatergic transmission in the accumbens in cue-induced responding for sucrose between adolescent and adult rats.
authors.affiliation: Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA.
authors.forename: S
authors.initials: S
authors.lastname: Myal
authors.affiliation: Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA.
authors.forename: P
authors.initials: P
authors.lastname: O'Donnell
authors.affiliation: Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA. Electronic address: d.s.counotte@gmail.com.
authors.forename: D S
authors.initials: DS
authors.lastname: Counotte
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives / Q000494:pharmacology; D000596:Amino Acids / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects*; D003463:Cues; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005247:Feeding Behavior / Q000187:drug effects; D008297:Male; D009714:Nucleus Accumbens / Q000187:drug effects*; D051381:Rats; D020318:Rats, Long-Evans; D012646:Self Administration; D013395:Sucrose / Q000008:administration & dosage*
chemical_list: D000596:Amino Acids; D019086:Bridged Bicyclo Compounds, Heterocyclic; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; C118218:LY 379268; C101185:alpha-methyl-4-phosphonophenylglycine; D013395:Sucrose; D000409:Alanine
keywords: adolescence; mGluR2/3; nucleus accumbens; reward; sucrose self-administration