In vivo occupancy of D2 dopamine receptors by nafadotride.
Nafadotride has been proposed as a selective antagonist for the D3 dopamine receptor. This drug has been shown to exhibit selectivity between D2 and D3 dopamine receptors in in vitro assay systems; however, the in vivo D2/D3 selectivity of the compound has not been determined. In this study, protection against inactivation by EEDQ was used as a measure of in vivo occupancy of D2 receptors by behaviorally relevant doses of nafadotride (0.1-10 mg/kg, s.c. and i.p.) in adult, male Sprague-Dawley rats. Ex vivo [3H]spiperone binding was then determined in striatal membranes, l-Nafadotride (10 mg/kg) protected 71% of D2 receptors after s.c. administration; 40% after i.p. administration. Protection of 13% of D2 receptors was observed at a dose of 3 mg/kg (s.c.). These data suggest that blockade of D2 receptors contributes to the pharmacological effects of nafadotride when administered at doses above 1 mg/kg (s.c.) or 3 mg/kg (i.p.).
Levant
B
B
Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City 66160-7417, USA.
Vansell
N R
NR
D000818:Animals; D018492:Dopamine Antagonists / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D008297:Male; D009281:Naphthalenes / Q000494:pharmacology*; D011759:Pyrrolidines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000187:drug effects*
D018492:Dopamine Antagonists; D009281:Naphthalenes; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2; C097285:nafadotride