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Original Article |
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Neuropsychopharmacology (1999) 20 119-130.10.1038/sj.npp.1395238
Guanfacine and Clonidine, Alpha2-Agonists, Improve Paired Associates Learning, but not Delayed Matching to Sample, in Humans
Pekka Jäkälä1 MD, Jouni Sirviö2 Ph.D, Minna Riekkinen1 MD, Esa Koivisto1 BSc, Kosti Kejonen1 BSc, Matti Vanhanen1 BSc and Paavo Riekkinen1 MD |
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1Department of Neuroscience and Neurology, University of Kuopio, Kuopio, Finland, and University Hospital of Kuopio, Kuopio, Finland; and University Hospital of Kuopio, Kuopio, Finland
2A.I. Virtanen Institute, University of Kuopio, Kuopio, Finland
Correspondence: Dr Paavo Riekkinen, Department of Neuroscience and Neurology, University and University Hospital of Kuopio, P.O.B. 1627, FIN-70211, Kuopio, Finland
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ABSTRACT
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The present study compares the effects of two alpha2-agonists, clonidine (0.5, 2, and 5  g/kg, PO) and guanfacine (7 and 29 g/kg, PO) in young healthy volunteers on their performance in visual paired associates learning (PAL) and delayed matching to sample (DMTS) visual short-term recognition memory tests. In the PAL test, clonidine 2 and guanfacine 29 g/kg improved the subjects' performance. In the DMTS test, clonidine at 5 g/kg delay-dependently impaired performance accuracy, and at 2 and 5 g/kg it also slowed responses. Guanfacine had no effect on DMTS test performance. Clonidine 5 and guanfacine 29 g/kg equally increased subjective feelings of sedation and reduced blood pressure. The results suggest that both clonidine and guanfacine facilitated PAL learning by improving "frontal strategies," but only clonidine disrupted "mnemonic processing" decreasing DMTS accuracy. The greater selectivity of guanfacine for alpha2A-adrenoceptor subtype may explain the different profile of action of the drugs.
Keywords: Learning and memory; Cognitive functions; Clonidine; Guanfacine; Noradrenaline; alpha2-Adrenoceptors |
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