The N-methyl-D-aspartate receptor blocker MK-801 prevents the facilitatory effects of naloxone and epinephrine on retention of inhibitory avoidance task in rats.
The aim of this study was to evaluate the interaction between N-methyl-D-aspartate (NMDA) receptors and the adrenergic and opioid systems in the modulation of inhibitory avoidance retention. Rats were trained and tested in the step-down inhibitory avoidance task (0.3 mA footshock). The training-test interval was 24 h. The animals received an i.p. injection of saline or MK-801 (0.0625 mg/kg) 30 min before training, and saline, epinephrine (25 micrograms/kg), or naloxone (0.4 mg/kg) i.p. immediately after training. In the saline-pretreated rats, epinephrine and naloxone enhanced memory retention. Pretraining MK-801 prevented the facilitatory effects of those treatments. The present findings suggest that the facilitation of learning by post-training epinephrine and naloxone is prevented by the pretraining NMDA receptor blockade.
Quevedo
J
J
Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
Moretto
A
A
Colvero
M
M
Roesler
R
R
Ferreira
M B
MB
D000322:Adrenergic Agonists / Q000494:pharmacology; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects* / Q000502:physiology; D016291:Dizocilpine Maleate / Q000494:pharmacology*; D004837:Epinephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D005260:Female; D008568:Memory / Q000187:drug effects / Q000502:physiology; D009270:Naloxone / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*
D000322:Adrenergic Agonists; D018691:Excitatory Amino Acid Antagonists; D009292:Narcotic Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D009270:Naloxone; D016291:Dizocilpine Maleate; D004837:Epinephrine