NMDA receptor antagonist MK-801 blocks learning of conditioned stimulus-unconditioned stimulus contiguity but not fear of conditioned stimulus in goldfish (Carassius auratus L.).
The blockade of learning of Pavlovian fear conditioning by the N-methyl-D-aspartic acid (NMDA)-receptor antagonist MK-801 was examined in 166 goldfish. In previously untrained fish, MK-801 blocked learning of a light-off or a tone conditioned stimulus (CS) paired with an electrical shock unconditioned stimulus (US). Pretraining on the light-off CS did not affect the rate of learning of the tone CS but protected the tone learning from disruption by MK-801. Switching from the light-off to the tone CS changed the identity of the CS but not its temporal contiguity with the US. Pretraining consisting of pseudoconditioning of the light-off CS did not protect subsequent tone learning from blockade by MK-801. Thus, the NMDA receptor functions are necessary for learning related to the temporal contiguity of the CS and US but not to the identity of the CS as a cue to the occurrence of the fearful effects of the US.
Davis
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Mental Health Research Institute, University of Michigan.
Klinger
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D000161:Acoustic Stimulation; D000818:Animals; D001143:Arousal / Q000187:drug effects / Q000502:physiology; D001245:Association Learning / Q000187:drug effects* / Q000502:physiology; D001288:Attention / Q000187:drug effects / Q000502:physiology; D003214:Conditioning, Classical / Q000187:drug effects* / Q000502:physiology; D016291:Dizocilpine Maleate / Q000494:pharmacology*; D005239:Fear / Q000187:drug effects* / Q000502:physiology; D006054:Goldfish; D011939:Mental Recall / Q000187:drug effects / Q000502:physiology; D010775:Photic Stimulation; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects* / Q000502:physiology
D016194:Receptors, N-Methyl-D-Aspartate; D016291:Dizocilpine Maleate