[Synaptic tagging and memory trace].
OBJECTIVE
To present a panorama of the main features and possible identity of the synaptic tag, such as to discuss some of its functional implications.


METHODS
Long-term potentiation (LTP) constitutes a very attractive synaptic/cellular memory model. LTP, like memory, can manifest itself early (essentially depending on the modification of pre-existing proteins at synapse) and late (depending on new protein synthesis). As LTP is a highly specific phenomenon, a dilemma arises: how can the proteins, required to plastic change stabilization, that are synthesized at the soma of a neuron containing thousands of synaptic contacts--all depending of the same nucleus--go to the appropriate synapses? In this review, we present some of the models that intend to explain this question, making emphasis on synaptic tagging hypothesis. Some of the main findings that have contributed to tagging hypothesis are exposed. The local protein synthesis and the activation of protein kinases are analyzed as candidates to be the synaptic tag. Additionally, some of the functional implications of synaptic tagging are discussed.


CONCLUSIONS
The synaptic tagging hypothesis offers a very flexible and reasonable solution to the specificity of long-lasting synaptic changes. Although some of the tagging features are known, the synaptic tag identity has not yet been elucidated. It seems that there is not a unique synaptic tag, but there are rather multiple molecular synaptic tags involved. Each of them might function as a synaptic tag under particular circumstances. Each might be differentially recruited by specific stimuli and mediate plasticity over different time domains.
López-Rojas
J
J
Departamento de Neurología Experimental, Instituto de Neurología y Neurocirugía de la Habana, La Habana, Cuba. erojas@infomed.sld.cu
Almaguer-Melián
W
W
Bergado-Rosado
J A
JA
D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D017774:Long-Term Potentiation / Q000502:physiology*; D008568:Memory / Q000502:physiology*; D008959:Models, Neurological; D009473:Neuronal Plasticity / Q000502:physiology; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure
D017868:Cyclic AMP-Dependent Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases