Capture of the Late Phase of Long-Term Potentiation within and across the Apical and Basilar Dendritic Compartments of CA1 Pyramidal Neurons: Synaptic Tagging Is Compartment Restricted

Abstract

Studies in the rodent hippocampus have demonstrated that when the late phase of long-term potentiation (L-LTP) is induced in a set of synapses by suprathreshold stimulation, L-LTP can also be expressed by other synapses receiving subthreshold stimulation, a phenomenon usually referred as "capture of L-LTP." Because the pyramidal neurons in the mammalian hippocampus have both apical and basal dendrites, we have now investigated whether capture of L-LTP, previously described only within the apical dendritic compartment, can also take place within the basilar dendritic compartment and, if so, whether capture can be accomplished from one dendritic compartment to the other. We found that capture of L-LTP can also occur within the basilar dendritic compartment and that the tagging signal that enables capture appears to be the same in both dendritic compartments. However, capture across compartments, between the apical and basilar dendrites, follows different rules and requires a stronger triggering stimulation than capture within a compartment. These results suggest that the tag appears specific to a compartment either apical or basilar and that an additional mechanism may be required to capture across compartments.

Synapse-specific stabilization of plasticity processes: The synaptic tagging and capture hypothesis revisited 10 years later

“…Also, neuromodulatory input, besides its role on modulation of synaptic processes, can play a major role in the activation of specific cascades of gene expression and facilitate synaptic plasticity changes in a cell-wide manner (Berke and Hyman, 2000;Reymann and Frey, 2007). Similar facilitatory effects have been also observed after enhancing CREB-dependent gene expression (Alarcon et al, 2006;Barco et al, 2002;Marie et al, 2005). Although all these facilitatory effects can be, and have been, interpreted in terms of enhancing synaptic capture, the facilitation observed might also rely, as discussed in section 2.2, on sensitization mechanisms.…”

“…In a recent study, we investigated whether capture of L-LTP, previously described only within the apical dendritic compartment, could also occur within the basilar dendritic compartment and, if so, whether capture could be accomplished from one dendritic compartment to the other (Alarcon et al, 2006). We observed capture of L-LTP within the basilar dendritic compartment and found that the tagging signal mediating synaptic capture appeared to be the same in both dendritic compartments (1xHFS).…”

“…The typical stimulation protocol (1xHFS) that usually evokes capture of L-LTP within the same dendritic compartment (basilar or apical) failed to do so across dendritic compartments. Instead, a stronger stimulation or marking signal (2xHFS) was needed to evoke capture of L-LTP across dendritic compartments (Alarcon et al, 2006) (Figure 2J). …”

“…However, based in the currently well established role of local protein synthesis in LTP (Sutton and Schuman, 2006) and the significant effect of protein synthesis inhibitors observed in more recent late-associativity studies both in the mouse hippocampus (Alarcon et al, 2006;Barco et al, 2002) and Aplysia neurons (Casadio et al, 1999), it seems reasonable to consider the contribution of protein synthesis-dependent mechanisms in synaptic capture of L-LTP.…”

“…The STC hypothesis revisited 30 differential distribution of gene products from the soma to basal and apical dendrites (Alarcon et al, 2006;Fonseca et al, 2004;Sajikumar et al, 2007a;Sajikumar et al, 2007b). In consequence, gene products induced by signals that reach the nucleus seem to be primarily distributed back into the same dendritic compartment where the activation cascade was initiated.…”