title: Novel object recognition memory: measurement issues and effects of MDMA self-administration following short inter-trial intervals.
abstract: The present study was undertaken to examine effects of self-administered MDMA on novel object exploration (NOR) memory. Self-administration was conducted during daily 2 h tests that continued until a total of 165 mg/kg was self-administered (range = 13-41 days for individual rats). Control rats were placed in the self-administration boxes during daily sessions but did not receive any drug. One or 10 weeks following the last self-administration session, memory was assessed using a standard NOR task. When exploration time was used as the dependent measure for the control rats, there was no consistent pattern of change as a function of inter-trial interval (ITI) and exploration times failed to reveal decay in the function relating exploration to ITI. When number of approaches was examined as a function of ITI, however, there was a preference for the novel object following the short ITIs (1-15 min) and the function relating preference to ITI decayed with longer ITIs. When tested 7 days following the last self-administration session, rats that self-administered MDMA failed to demonstrate NOR even following the shortest ITI of 1 min. The data support the idea that MDMA self-administration produces cognitive deficits and are consistent with the idea that attentional processes become disrupted. There was, however, recovery of NOR memory when rats were tested following an extended drug-free period of 70 days. Thus, the deficits are transient and recovery was apparent.
authors.affiliation: School of Psychology, Victoria University of Wellington, Wellington, New Zealand. susan.schenk@vuw.ac.nz
authors.forename: Susan
authors.initials: S
authors.lastname: Schenk
authors.forename: David N
authors.initials: DN
authors.lastname: Harper
authors.forename: Jennifer
authors.initials: J
authors.lastname: Do
mesh_terms: D000818:Animals; D005106:Exploratory Behavior / Q000187:drug effects; D006213:Hallucinogens / Q000008:administration & dosage / Q000633:toxicity*; D008297:Male; D008569:Memory Disorders / Q000139:chemically induced*; D018817:N-Methyl-3,4-methylenedioxyamphetamine / Q000008:administration & dosage / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D021641:Recognition, Psychology / Q000187:drug effects*; D012646:Self Administration; D013997:Time Factors
chemical_list: D006213:Hallucinogens; D018817:N-Methyl-3,4-methylenedioxyamphetamine