Memory facilitation by naloxone is due to release of dopaminergic and beta-adrenergic systems from tonic inhibition.
The post-training IP administration of naloxone (0.8 mg/kg) facilitates memory consolidation of the habituation of a rearing response to a tone in rats. Amphetamine (1.0 - 2.5 mg/kg or nicotine (0.2 - 0.5 mg/kg), and amphetamine (2.5 mg/kg) plus nicotine (0.5 mg/kg) have no effect. The higher doses of amphetamine or nicotine, however, when given together with a dose of naloxone which is ineffective alone (0.2 mg/kg), markedly enhance consolidation. Haloperidol (0.5 mg/kg), propranolol (0.5 mg/kg), and phenoxybenzamine (2.0 mg/kg) have no effect on their own; whereas tolazoline (2.0 mg/kg) impairs consolidation. The effect of naloxone (0.8 mg/kg) is antagonized by haloperidol and by propranolol, but not by phenoxybenzamine or tolazoline. The results suggest that naloxone causes memory facilitation through the release of central dopaminergic and beta-adrenergic mechanisms from a tonic inhibitory influence of endogenous opiate peptide systems.
D000818:Animals; D003913:Dextroamphetamine / Q000494:pharmacology; D004298:Dopamine / Q000502:physiology*; D004347:Drug Interactions; D005260:Female; D006220:Haloperidol / Q000494:pharmacology; D008568:Memory / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology*; D009433:Neural Inhibition / Q000187:drug effects*; D009538:Nicotine / Q000494:pharmacology; D010643:Phenoxybenzamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects* / Q000502:physiology; D014043:Tolazoline / Q000494:pharmacology
D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D010643:Phenoxybenzamine; D009270:Naloxone; D009538:Nicotine; D011433:Propranolol; D014043:Tolazoline; D006220:Haloperidol; D003913:Dextroamphetamine; D004298:Dopamine