title: D1 agonist dihydrexidine releases acetylcholine and improves cognitive performance in rats.
abstract: Dihydrexidine is a selective, full-efficacy dopamine D1 receptor agonist that has displayed therapeutic potential in Parkinson's disease by reversing motor deficits of MPTP-treated monkeys. The present study monitored the effects of dihydrexidine on acetylcholine release in rat brain by using in vivo microdialysis. Moderate doses of dihydrexidine [3 and 10 mg/kg, intraperitoneally (I.P.)] elevated extracellular concentrations of acetylcholine by 40-60% in rat striatum; higher doses did not significantly alter acetylcholine release. SCH 23390 blocked the dihydrexidine-induced increase, indicating a D1 receptor-mediated action. A more robust stimulatory effect of dihydrexidine on acetylcholine release was observed in prefrontal cortex (to 300% of basal output) than in striatum. Dihydrexidine was also evaluated in a passive avoidance procedure in rats to determine if its neurochemical effects translated into cognition-enhancing activity; in this assay, dihydrexidine (0.3 mg/kg, I.P.) significantly improved the scopolamine-induced deficits. The results of these studies suggest that the acetylcholine-releasing properties of dihydrexidine and other D1 agonists may underlie their cognition-enhancing activity and thus may have clinical value in the treatment of dementia.
authors.affiliation: Interneuron Pharmaceuticals Inc., Lexington, Massachusetts 02173, USA.
authors.forename: T D
authors.initials: TD
authors.lastname: Steele
authors.forename: D B
authors.initials: DB
authors.lastname: Hodges
authors.forename: T R
authors.initials: TR
authors.lastname: Levesque
authors.forename: K W
authors.initials: KW
authors.lastname: Locke
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D003071:Cognition / Q000187:drug effects*; D018491:Dopamine Agonists / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D008297:Male; D017551:Microdialysis; D010617:Phenanthridines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D018491:Dopamine Agonists; D010617:Phenanthridines; C061532:dihydrexidine; D000109:Acetylcholine