Persistent increased PKM in long-term and remote spatial memory
NEUROBIOLOGY OF LEARNING AND MEMORY
Authors: Hsieh, Changchi; Tsokas, Panayiotis; Serrano, Peter; Hernandez, A. Ivan; Tian, Dezhi; Cottrell, James E.; Shouval, Harel Z.; Fenton, Andre Antonio; Sacktor, Todd Charlton
Abstract
PKM zeta is an autonomously active PKC isoform that is thought to maintain both LTP and long-term memory. Whereas persistent increases in PKM zeta protein sustain the kinase's action in LTP, the molecular mechanism for the persistent action of PKM zeta during long-term memory has not been characterized. PKM zeta inhibitors disrupt spatial memory when introduced into the dorsal hippocampus from 1 day to 1 month after training. Therefore, if the mechanisms of PKM zeta's persistent action in LTP maintenance and longterm memory were similar, persistent increases in PKM zeta would last for the duration of the memory, far longer than most other learning-induced gene products. Here we find that spatial conditioning by aversive active place avoidance or appetitive radial arm maze induces PKM zeta increases in dorsal hippocampus that persist from 1 day to 1 month, coinciding with the strength and duration of memory retention. Suppressing the increase by intrahippocampal injections of PKW-antisense oligodeoxynucleotides prevents the formation of long-term memory. Thus, similar to LTP maintenance, the persistent increase in the amount of autonomously active PKM zeta sustains the kinase's action during long-term and remote spatial memory maintenance. (C) 2016 Published by Elsevier Inc.
Loss of Synaptic Tagging in the Anterior Cingulate Cortex after Tail Amputation in Adult Mice
JOURNAL OF NEUROSCIENCE
Authors: Liu, Ming-Gang; Song, Qian; Zhuo, Min
Abstract
Anterior cingulate cortex (ACC) is known to play important roles in key brain functions such as pain perception, cognition, and emotion. Different forms of homosynaptic plasticity such as long-term potentiation (LTP) and long-term depression have been studied in ACC synapses. However, heterosynaptic plasticity such as synaptic tagging has not been reported. Here, we demonstrate synaptic tagging in the ACC of adult male mice by using a 64-channel multielectrode array recording system. Weak theta burst stimulation (TBS), normally inducing early-phase LTP or No-LTP in most of the activated channels, produced late phase-LTP (L-LTP) in a majority of channels when a strong TBS was applied earlier to a separate input within a certain time window. Similar to hippocampus, synaptic tagging in the ACC depends on the synthesis of new proteins. Tail amputation-induced peripheral injury caused a loss of this heterosynaptic L-LTP and occluded strong TBS-evoked L-LTP as well. Together, we provide the first report of the synaptic tagging-like phenomenon in the ACC of adult mice, and the loss of synaptic tagging to amputation may contribute to injury-related cognitive changes and phantom limb sensation and pain.