Methadone disrupts performance on the working memory version of the Morris water task.
The aim of the study was to examine if administration of the mu-opiate agonist methadone hydrochloride resulted in deficits in performance on the Morris water tank task, a widely used test of spatial cognition. To this end, after initial training on the task, Long-Evans rats were administered saline or methadone at either 1.25, 2.5 or 5 mg/kg ip 15 min prior to testing. The performance of the highest-dose methadone group was inferior to that of the controls on the working memory version of the Morris task. There were also differences between the groups on the reference memory version of the task, but this result cannot be considered reliable. These data show that methadone has its most profound effect on cognition in rats when efficient performance on the task requires attention to and retention of new information, in this case, the relationship between platform location and the extramaze cues.
Hepner
Ilana J
IJ
Department of Psychology, Macquarie University, 2109 Sydney, Australia.
Homewood
Judi
J
Taylor
Alan J
AJ
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001835:Body Weight / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D008297:Male; D018782:Maze Learning / Q000187:drug effects*; D008568:Memory / Q000502:physiology; D008570:Memory, Short-Term / Q000187:drug effects*; D008691:Methadone / Q000494:pharmacology*; D011597:Psychomotor Performance / Q000187:drug effects*; D051381:Rats; D020318:Rats, Long-Evans
D000701:Analgesics, Opioid; D008691:Methadone