Long-term memory formation in the chick requires mobilization of ryanodine-sensitive intracellular calcium stores.
Training chicks (Gallus domesticus) on a one-trial passive avoidance task results in transient and time-dependent enhanced increases in N-methyl-d-aspartate- or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate-stimulated intracellular calcium concentration in synaptoneurosomes isolated from a specific forebrain region, the intermediate medial hyperstriatum ventrale. This increase could result from either calcium entry from the extracellular medium or from mobilization of intracellular calcium stores. We have therefore examined the effects of dantrolene, an inhibitor of calcium release from the intracellular ryanodine-sensitive store, on these processes. Dantrolene, 50 nmol per hemisphere injected intracerebrally 30 min pre- or 30 min posttraining, blocked longer term memory for the passive avoidance task, whereas memory for the task was unaffected when dantrolene was injected at earlier or later times. Preincubation of synaptoneurosomes, isolated from the intermediate hyperstriatum ventrale 10 min after training, with 100 nM dantrolene abolished the enhanced training-induced increase in intracellular calcium concentration elicited by 0.5 mM N-methyl-d-aspartate. By contrast, the training-induced enhancement of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate-stimulated increase in intracellular calcium concentration in synaptoneurosomes prepared 6 h posttraining was unaffected by preincubation with dantrolene, which was not amnestic at this time. Calcium release from ryanodine-sensitive intracellular stores may thus be a necessary stage in the early phase of the molecular cascade leading to the synaptic modulation required for long-term memory storage.
Salinska
E J
EJ
Department of Neurochemistry, Medical Research Centre, Pawinskiego 5, Warsaw, 02-106, Poland.
Bourne
R C
RC
Rose
S P
SP
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D001522:Behavior, Animal / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002645:Chickens; D003620:Dantrolene / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D007306:Insecticides / Q000494:pharmacology*; D017136:Ion Transport / Q000187:drug effects; D008568:Memory / Q000187:drug effects*; D009125:Muscle Relaxants, Central / Q000494:pharmacology; D016202:N-Methylaspartate / Q000378:metabolism / Q000494:pharmacology; D016548:Prosencephalon / Q000187:drug effects; D012433:Ryanodine / Q000494:pharmacology*; D013574:Synaptosomes / Q000187:drug effects; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000378:metabolism / Q000494:pharmacology
D018690:Excitatory Amino Acid Agonists; D007306:Insecticides; D009125:Muscle Relaxants, Central; D012433:Ryanodine; D016202:N-Methylaspartate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D003620:Dantrolene; D002118:Calcium