title: Effects of metabotropic glutamate receptor 5 on latent inhibition in conditioned taste aversion.
abstract: Latent inhibition (LI) is a phenomenon by which pre-exposure of a conditioned stimulus (CS) prior to the CS-unconditioned stimulus (US) pairings retards conditioned responding (CR). LI has been demonstrated in a variety of learning tasks including conditioned taste aversion (CTA). Earlier work has shown that systemic administration of 2-methyl-6-(phenylethynyl)-pyridine (MPEP), a selective metabotropic glutamate receptor 5 (mGlu5) antagonist, is able to disrupt classical conditioning in CTA. The present study investigated the involvement of mGlu5 receptors in LI using a CTA procedure. In the first experiment, rats received either water (non-pre-exposed, NPE) or a saccharin solution (pre-exposed, PE) on 2 consecutive days. The animals then received conditioning in which a fixed amount of saccharin was paired with lithium chloride and then the CR to the taste was tested. Either MPEP (3, 6, 12 mg/kg) or vehicle was injected intraperitoneally prior to taste pre-exposure or testing. Animals in the vehicle control groups displayed LI. MPEP injections before pre-exposure trials attenuated LI but also reduced consumption during pre-exposure, which obscured interpretation of the LI effect. The second experiment used four pre-exposure trials and controlled access to fixed amount of the solutions during the pre-exposure as well as the conditioning trials. Rats were injected before pre-exposure trials but not before the test trial. The results found that MPEP attenuates latent inhibition suggesting that the mGlu5 receptor exerts an influence on the processes that underlie the effects of taste pre-exposure on conditioning.
authors.affiliation: Department of Psychological Sciences, University of Missouri, Columbia, MO 65211, USA.
authors.forename: Carla
authors.initials: C
authors.lastname: Bills
authors.forename: Todd R
authors.initials: TR
authors.lastname: Schachtman
authors.forename: Peter
authors.initials: P
authors.lastname: Serfozo
authors.forename: Will P J M
authors.initials: WP
authors.lastname: Spooren
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Gasparini
authors.forename: Agnes
authors.initials: A
authors.lastname: Simonyi
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology*; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D007266:Inhibition, Psychological; D008297:Male; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects / Q000502:physiology*; D013649:Taste / Q000187:drug effects / Q000502:physiology*
chemical_list: D018691:Excitatory Amino Acid Antagonists; D011725:Pyridines; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; C121465:6-methyl-2-(phenylethynyl)pyridine