Does chronic prenatal methadone exposure affect beta-receptor subtypes in placental, fetal and maternal brain homogenates?
Computer competition analysis of 3H-DHA (3H-dihydroalprenolol, a nonselective beta-adrenergic radioligand) binding in the presence of unlabeled metoprolol (a beta 1-selective antagonist) indicates the existence of both beta 1- and beta 2-adrenergic receptor subtypes in the rat placenta and confirms previous reports that both beta-adrenoceptors are present in adult rat cortex. In the fetal brain (20th day of gestation), however, only beta 1-receptors were detected. Pregnant rats were chronically exposed to methadone from day 7 to day 20 of gestation via implanted osmotic minipumps (6.3-9.0 mg/kg/day). This treatment schedule did not induce a change in the affinity and density of either beta-receptor subtype in the placental, fetal and maternal brain homogenates. The results are discussed in terms of the reported monoaminergic and opiate receptor functional interactions.
Darmani
N A
NA
Department of Pharmacology/Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298.
Schnoll
S H
SH
Fuchs
B
B
Martin
B R
BR
D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D004082:Dihydroalprenolol / Q000378:metabolism; D005260:Female; D005333:Fetus / Q000187:drug effects / Q000378:metabolism; D008431:Maternal-Fetal Exchange; D008691:Methadone / Q000633:toxicity*; D008790:Metoprolol / Q000378:metabolism; D010920:Placenta / Q000187:drug effects / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000145:classification / Q000187:drug effects* / Q000378:metabolism
D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; D008790:Metoprolol; D008691:Methadone