title: Memory-enhancing treatments do not reverse the impairment of inhibitory avoidance retention induced by NMDA receptor blockade.
abstract: The aim of the present research was to verify whether the impairment of retention induced by the N-methyl-d-aspartate (NMDA) receptor blocker (+)-10,11-dihydro-5-methyl-5H-dibenzo[a,d]cycloheptene-5,10 imine (MK-801) can be reversed by memory-enhancing treatments. Adult female Wistar rats were trained and tested in a step-down inhibitory avoidance task (0.3-mA foot shock, 24-h training-test interval). Animals were given an ip injection of saline (SAL) or MK-801 (0.0625 mg/kg) 30 minutes before training, and an ip injection of SAL, epinephrine (EPI) (25 microg/kg), the opioid receptor antagonist naloxone (NAL) (0.4 mg/kg), the glucocorticoid receptor agonist dexamethasone (DEX) (0.3 mg/kg), or glucose (GLU) (320 mg/kg) immediately after training. There was an impairment of inhibitory avoidance retention in the MK-801-SAL, MK-801-EPI, MK-801-NAL, MK-801-DEX, and MK-801-GLU groups. There was an enhancement of retention in the SAL-EPI, SAL-NAL, SAL-DEX, and SAL-GLU groups. A control experiment showed that the amnestic effects of MK-801 could not be attributed to decreased reactivity to the foot shock. The results suggest that memory-enhancing treatments directed at modulatory mechanisms do not reverse the memory impairment induced by NMDA receptor blockade.
authors.affiliation: Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul (Campus da Saúde), Porto Alegre, RS, 90035-003, Brazil. roesler@vortex.ufrgs.br
authors.forename: R
authors.initials: R
authors.lastname: Roesler
authors.forename: M R
authors.initials: MR
authors.lastname: Vianna
authors.forename: F
authors.initials: F
authors.lastname: de-Paris
authors.forename: J
authors.initials: J
authors.lastname: Quevedo
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D001921:Brain / Q000187:drug effects; D003907:Dexamethasone / Q000494:pharmacology; D016291:Dizocilpine Maleate / Q000037:antagonists & inhibitors*; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D005950:Glucose Solution, Hypertonic / Q000494:pharmacology; D011939:Mental Recall / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology; D009433:Neural Inhibition / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D011957:Receptors, Opioid / Q000187:drug effects; D012153:Retention, Psychology / Q000187:drug effects*
chemical_list: D005950:Glucose Solution, Hypertonic; D016194:Receptors, N-Methyl-D-Aspartate; D011957:Receptors, Opioid; D009270:Naloxone; D016291:Dizocilpine Maleate; D003907:Dexamethasone; D004837:Epinephrine