Post-trial NMDA receptor allosteric blockade differentially influences habituation of behavioral responses to novelty in the rat.
The involvement of glutamatergic receptors of the N-methyl-D-aspartate (NMDA) type in long-term behavioral habituation (LTH) to a novel environment was investigated. To this aim, adult male Sprague-Dawley rats were first exposed to a Làt-maze. Horizontal (corner-crossings) and vertical activity (rearings) were measured per 1-min block. Immediately after a 10-min test trial in the maze, rats were systemically injected with either 6 or 20 mg/kg of the allosteric NMDA receptor blocker ketamine-HCl (KET) or vehicle. Retention was tested one week later. LTH was expressed as the decline in horizontal and vertical activity from test trial 1 to test trial 2. The results showed a facilitation of the two components of LTH at 6 mg/kg and a disruption at 20 mg/kg. This biphasic effect pertained to vertical activity only. For both activity components, the facilitation of LTH at 6 mg/kg pertained to the first part, whereas the inhibition at 20 mg/kg pertained to the second part of the testing period. Since horizontal and vertical activity are thought to have a prevailing cognitive (spatial) and non-cognitive (emotional) meaning, subanesthetic doses of KET differentially affect the long-lasting retention of these behavioral responses to novelty. Thus, NMDA receptors seem to be involved in the coupling of spatial and emotional components of information.
Gironi Carnevale
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UA
Institute of Human Physiology and Biomedical Physics, First Medical School, University of Naples, Italy.
Vitullo
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E
Sadile
A G
AG
D000818:Animals; D001143:Arousal / Q000187:drug effects*; D001921:Brain / Q000187:drug effects*; D004193:Discrimination Learning / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005106:Exploratory Behavior / Q000187:drug effects; D006185:Habituation, Psychophysiologic / Q000187:drug effects*; D007649:Ketamine / Q000494:pharmacology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009949:Orientation / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter / Q000187:drug effects*; D012931:Social Environment
D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter; D007649:Ketamine