title: Effects of adolescent exposure to methylmercury and d-amphetamine on reversal learning and an extradimensional shift in male mice.
abstract: Adolescence is associated with the continued maturation of dopamine neurotransmission and is implicated in the etiology of many psychiatric illnesses. Adolescent exposure to neurotoxicants that distort dopamine neurotransmission, such as methylmercury (MeHg), may modify the effects of chronicd-amphetamine (d-AMP) administration on reversal learning and attentional-set shifting. Male C57Bl/6n mice were randomly assigned to two MeHg-exposure groups (0 ppm and 3 ppm) and twod-AMP-exposure groups (saline and 1 mg/kg/day), producing four treatment groups (n = 10-12/group): control, MeHg, d-AMP, and MeHg +d-AMP. MeHg exposure (via drinking water) spanned postnatal days 21-59 (the murine adolescent period), and once daily intraperitoneal injections ofd-AMP or saline spanned postnatal days 28-42. As adults, mice were trained on a spatial-discrimination-reversal (SDR) task in which the spatial location of a lever press predicted reinforcement. Following 2 SDRs, a visual-discrimination task (extradimensional shift) was instated in which the presence of a stimulus light above a lever predicted reinforcement. Responding was modeled using a logistic function, which estimated the rate (slope) of a behavioral transition and trials required to complete half a transition (half-max). MeHg,d-AMP, and MeHg +d-AMP exposure increased estimates of half-max on the second reversal. MeHg exposure increased half-max and decreased the slope term following the extradimensional shift, but these effects did not occur following MeHg +d-AMP exposure. MeHg +d-AMP exposure produced more perseverative errors and omissions following a reversal. Adolescent exposure to MeHg can modify the behavioral effects of chronicd-AMP administration. (PsycINFO Database Record
authors.affiliation: Department of Psychology.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Boomhower
authors.affiliation: Department of Psychology.
authors.forename: M Christopher
authors.initials: MC
authors.lastname: Newland
mesh_terms: D000367:Age Factors; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003913:Dextroamphetamine / Q000008:administration & dosage / Q000494:pharmacology*; D004193:Discrimination Learning / Q000187:drug effects; D004298:Dopamine / Q000378:metabolism*; D007274:Injections, Intraperitoneal; D008297:Male; D008767:Methylmercury Compounds / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D011897:Random Allocation; D012054:Reinforcement, Psychology; D012193:Reversal Learning / Q000187:drug effects*
chemical_list: D008767:Methylmercury Compounds; D003913:Dextroamphetamine; D004298:Dopamine