Amnesia Research Today is a free monthly online journal that collates and summarizes the latest research about Amnesia, including details on memory loss, causes, treatment, brain injury,. | ||||||||
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Dopamine D3 receptor antagonists improve the learning performance in memory-impaired rats.Laszy J, Laszlovszky I, Gyertyán I Department of Behavioural Pharmacology, Gedeon Richter Ltd, P.O.B. 27, Budapest, Hungary, 1475. j.laszy@richter.hu RATIONALE: The dopamine D3 receptor has been extensively studied in animal models of drug abuse and psychosis; however, less is known on its possible role in cognitive functions. OBJECTIVES: This study investigated the effects of different D3 antagonists and a partial agonist on spatial learning performance in a water labyrinth test. METHODS: Rats had to swim through a labyrinth system by making correct directional turns at three choice-points. The number of errors was recorded in three daily trials for 3 days. RESULTS: D3 antagonists such as the highly selective SB-277011 (24 mg/kg p.o.) and RGH-1756 (1 mg/kg p.o.), the moderately selective U-99194A (12 mg/kg s.c.) and the selective partial D3 agonist BP-897 (1 mg/kg i.p.) all significantly attenuated the learning deficit caused by FG-7142. Against scopolamine-induced amnesia, SB-277011 (24 mg/kg p.o.) was equally potent in showing protective efficacy; however, two times higher dose levels of U-99194A (24 mg/kg s.c.) and RGH-1756 (2 mg/kg p.o.) were required to attenuate the scopolamine-induced impairment. In contrast to the full antagonists, against scopolamine-induced amnesia, the partial agonist BP-897 (2 mg/kg i.p.) was inactive, even at the two times higher dose level. CONCLUSIONS: These data suggest that dopamine D3 receptor antagonists possess cognition-enhancing activity which may be of benefit in the treatment of cognitive dysfunction associated with several psychiatric disorders. Published 2 May 2005 in Psychopharmacology (Berl), 179(3): 567-75.
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