Interaction between paired-pulse facilitation and long-term potentiation in the projection from hippocampal area CA1 to the entorhinal cortex

Abstract

The hippocampus communicates with the neocortex via the entorhinal cortex and is thought to be critically involved in the consolidation of memories. This paper contains in vivo evidence of a projection from the hippocampal area CA1 to the entorhinal cortex. Current theories of memory formation suggest that the backprojections from the hippocampus to the neocortex should undergo some form of plastic change in order that memories become consolidated. Paired-pulse facilitation (PPF) and long-term potentiation (LTP) are forms of short- and long-term plasticity, respectively. We show that the CA1 to entorhinal cortex projection is capable of sustaining PPF over a wide range of stimulus intervals. In addition we demonstrate that following high frequency stimulation of this pathway the evoked response in the entorhinal cortex remains potentiated for at least 30 min. Finally, we demonstrate that PPF changes following LTP depending on the initial ratio of PPF, suggesting that LTP expression on this pathway may contain a presynaptic component. These findings should provide insight into the hippocampal function in memory formation.

Antagonism of glutamate receptors in the CA1 to perirhinal cortex projection prevents long-term potentiation and attenuates levels of brain-derived neurotrophic factor

“…This finding has important implications both in terms of memory research and the spread of epileptiform activity generated in the hippocampal regions. Indeed, this combined with our previous work demonstrating the capabilities of the CA1 to entorhinal cortex and subiculum to entorhinal cortex projections of sustaining plasticity (Craig and Commins, 2005; suggests multiple routes by which long-term memory can be consolidated in the neocortex. As area CA1 is one of the primary output structures of the hippocampus (Van Groen and Fig.…”

“…The perirhinal cortex also provides excitatory inputs to both the area CA1 and the subiculum (Naber et al, 1999;2001b). In addition, the perirhinal cortex can connect with the hippocampus through reciprocal connections with the entorhinal cortex (Burwell and Amaral, 1998a;1998b;Burwell, 2001) and the entorhinal cortex is in turn reciprocally connected to the hippocampus (Deacon et al, 1983;Kloosterman et al, 2003;Craig and Commins, 2005;. Despite these studies there has been little work describing either the electrophysiological or the pharmacological properties of these projections.…”

“…Despite these studies there has been little work describing either the electrophysiological or the pharmacological properties of these projections. Recently, Craig and Commins (2005; have reported that projections from both the area CA1 and the subiculum to the entorhinal cortex can sustain LTP while Cousens and Otto (1998) succeeded in inducing LTP in the CA1 to perirhinal cortex projection using theta burst stimulation (TBS). Initial work in our lab supports the findings of Cousens and Otto; the CA1 to perirhinal pathway can sustain LTP for at least an hour following 250 Hz high-frequency stimulation (HFS) (Kealy and Commins, unpublished observations), suggesting that the pathway going from the area CA1 to the perirhinal cortex is electrophysiologically active and could play a role in memory formation.…”

P1‐178: Early astrocytic atrophy in the Entorhinal cortex of a triple transgenic animal model of Alzheimer's disease

“…The EC is also essential for memory consolidation (Remondes and Schuman, 2004;Craig and Commins, 2005) and spatial navigation and memory (Fyhn et al, 2004;Moser et al, 2008).…”

Tenuigenin enhances hippocampal Schaffer collateral-CA1 synaptic transmission through modulating intracellular calcium

“…* * p < 0.01 as compared with the control. Each group n = 8. dependent on presynaptic mechanisms (Craig and Commins 2005;Zucker and Regehr 2002). Additionally, PPF is a dynamic enhancement of transmitter release considered crucial in CNS information processing.…”