Effects of beta-adrenergic blocking agents on specific binding of [3H]D-Ala2-Met5-enkephalinamide and [3H]naloxone.
To gain further insight into the central nervous system (CNS)-action of beta-adrenergic blocking agents (beta-blockers), we examined the effects of various kinds of beta-blockers on opioid receptors (Op-Rs) using radiolabeled receptor assay (RRA). We demonstrated that beta-blockers are competitively bound to Op-Rs in the CNS. Sodium index of beta-blockers in [3H]naloxone binding study indicated that beta-blockers had the mixed agonist-antagonist activity of opiates. The relative potency of beta-blockers in opioid RRA was negatively correlated with their membrane stabilizing activity. Neither beta-blocking activity nor intrinsic sympathomimetic activity was correlated with IC50 values of beta-blockers in opioid RRA. While it is widely accepted that beta-blockers have a tranquilizing activity, a part of the tranquilizing action of beta-blockers may be mediated through Op-Rs in the CNS. Although beta-blockers may have effects on their own receptors (beta-receptors) in the CNS, the more precise mechanisms of central action of these drugs must be further investigated.
Third Department of Internal Medicine, Okayama University Medical School, Japan.
H
H
Takayama
N
N
Ogawa
M
M
Asanuma
H
H
Hirata
T
T
Ogura
Z
Z
Ota
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives* / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009270:Naloxone / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects; D012964:Sodium / Q000494:pharmacology
D000319:Adrenergic beta-Antagonists; D011957:Receptors, Opioid; D009270:Naloxone; D004744:Enkephalin, Methionine; C022118:enkephalinamide-Met, Ala(2)-; D012964:Sodium