skip to main content

Title: Structural plasticity of dendritic secretorycompartments during LTP-inducedsynaptogenesis
Long-term potentiation (LTP), an increase in synaptic efficacy following high-frequencystimulation, is widely considered a mechanism of learning. LTP involves local remodeling ofdendritic spines and synapses. Smooth endoplasmic reticulum (SER) and endosomal compartmentscould provide local stores of membrane and proteins, bypassing the distant Golgi apparatus. Totest this hypothesis, effects of LTP were compared to control stimulation in rat hippocampal areaCA1 at postnatal day 15 (P15). By two hours, small spines lacking SER increased after LTP, whereaslarge spines did not change in frequency, size, or SER content. Total SER volume decreased afterLTP consistent with transfer of membrane to the added spines. Shaft SER remained more abundantin spiny than aspiny dendritic regions, apparently supporting the added spines. Recyclingendosomes were elevated specifically in small spines after LTP. These findings suggest localsecretory trafficking contributes to LTP-induced synaptogenesis and primes the new spines forfuture plasticity.
Authors:
Award ID(s):
1707356
Publication Date:
NSF-PAR ID:
10171017
Journal Name:
ELife
ISSN:
1592-3789
Sponsoring Org:
National Science Foundation
More Like this
  1. Analysis of long-term potentiation (LTP) provides a powerful window into cellular mechanisms of learning and memory. Prior work shows late LTP (L-LTP), lasting three or more hours, first occurs at postnatal day 12 (P12) in Long-Evans rat hippocampus. The goal of the current work was to determine the developmental onset of L-LTP in mouse hippocampus as a basis for comparing potential effects of key genetic manipulations known to affect dendritic spine structure. Four mouse strains were tested. Both C57BL/6 and Fmr1-/y mice on the C57BL/6 background began to show reliable L-LTP at P35. In contrast, both 129SVE wild type andmore »Hevin- /- (Sparcl1-/-) on the 129SVE background first showed reliable L-LTP at P28. All strains showed a gradual progression between P10 to P28 in success rate for short-term potentiation (STP), which lasts one hour or less. At P10 in rats, two episodes of TBS result in L-LTP when he time between episodes was > 90 minutes. In mice, multiple bouts of TBS at various inter-bout intervals did not advance the onset age of L-LTP. Prior work in rats showed the onset of L-LTP at P12 coincided with the first formation of dendritic spines. In contrast, hippocampal dendritic spines are present by P24 in C57BL/6 mice, well before the onset age for L-LTP. These speciesdependent findings suggest that dendritic spines may be necessary but not sufficient for L-LTP.« less
  2. Abstract
    Excessive phosphorus (P) applications to croplands can contribute to eutrophication of surface waters through surface runoff and subsurface (leaching) losses. We analyzed leaching losses of total dissolved P (TDP) from no-till corn, hybrid poplar (Populus nigra X P. maximowiczii), switchgrass (Panicum virgatum), miscanthus (Miscanthus giganteus), native grasses, and restored prairie, all planted in 2008 on former cropland in Michigan, USA. All crops except corn (13 kg P ha−1 year−1) were grown without P fertilization. Biomass was harvested at the end of each growing season except for poplar. Soil water at 1.2 m depth was sampled weekly to biweekly for TDP determination during March–November 2009–2016More>>
  3. An approach combining signal detection theory and precise 3D reconstructions from serial section electron microscopy (3DEM) was used to investigate synaptic plasticity and information storage capacity at medial perforant path synapses in adult hippocampal dentate gyrus in vivo. Induction of long-term potentiation (LTP) markedly increased the frequencies of both small and large spines measured 30 minutes later. This bidirectional expansion resulted in heterosynaptic counterbalancing of total synaptic area per unit length of granule cell dendrite. Control hemispheres exhibited 6.5 distinct spine sizes for 2.7 bits of storage capacity while LTP resulted in 12.9 distinct spine sizes (3.7 bits). In contrast,more »control hippocampal CA1 synapses exhibited 4.7 bits with much greater synaptic precision than either control or potentiated dentate gyrus synapses. Thus, synaptic plasticity altered total capacity, yet hippocampal subregions differed dramatically in their synaptic information storage capacity, reflecting their diverse functions and activation histories.« less
  4. Long-term potentiation (LTP) is a cellular mechanism of learning and memory that results in a sustained increase in the probability of vesicular release of neurotransmitter. However, previous work in hippocampal area CA1 of the adult rat revealed that the total number of vesicles per synapse decreases following LTP, seemingly inconsistent with the elevated release probability. Here, electron-microscopic tomography (EMT) was used to assess whether changes in vesicle density or structure of vesicle tethering filaments at the active zone might explain the enhanced release probability following LTP. The spatial relationship of vesicles to the active zone varies with functional status. Tightlymore »docked vesicles contact the presynaptic membrane, have partially formed SNARE complexes, and are primed for release of neurotransmitter upon the next action potential. Loosely docked vesicles are located within 8 nm of the presynaptic membrane where SNARE complexes begin to form. Nondocked vesicles comprise recycling and reserve pools. Vesicles are tethered to the active zone via filaments composed of molecules engaged in docking and release processes. The density of tightly docked vesicles was increased 2 h following LTP compared to control stimulation, whereas the densities of loosely docked or nondocked vesicles congregating within 45 nm above the active zones were unchanged. The tethering filaments on all vesicles were shorter and their attachment sites shifted closer to the active zone. These findings suggest that tethering filaments stabilize more vesicles in the primed state. Such changes would facilitate the long-lasting increase in release probability following LTP.

    « less
  5. To better understand temperature's role in the interaction between local evolutionary adaptation and physiological plasticity, we investigated acclimation effects on metabolic performance and thermal tolerance among natural Fundulus heteroclitus (small estuarine fish) populations from different thermal environments. Fundulus heteroclitus populations experience large daily and seasonal temperature variations, as well as local mean temperature differences across their large geographical cline. In this study, we use three populations: one locally heated (32°C) by thermal effluence (TE) from the Oyster Creek Nuclear Generating Station, NJ, and two nearby reference populations that do not experience local heating (28°C). After acclimation to 12 or 28°C,more »we quantified whole-animal metabolic (WAM) rate, critical thermal maximum (CT max ) and substrate-specific cardiac metabolic rate (CaM, substrates: glucose, fatty acids, lactate plus ketones plus ethanol, and endogenous (i.e. no added substrates)) in approximately 160 individuals from these three populations. Populations showed few significant differences due to large interindividual variation within populations. In general, for WAM and CT max , the interindividual variation in acclimation response (log 2 ratio 28/12°C) was a function of performance at 12°C and order of acclimation (12–28°C versus 28–12°C). CT max and WAM were greater at 28°C than 12°C, although WAM had a small change (2.32-fold) compared with the expectation for a 16°C increase in temperature (expect 3- to 4.4-fold). By contrast, for CaM, the rates when acclimatized and assayed at 12 or 28°C were nearly identical. The small differences in CaM between 12 and 28°C temperature were partially explained by cardiac remodeling where individuals acclimatized to 12°C had larger hearts than individuals acclimatized to 28°C. Correlation among physiological traits was dependent on acclimation temperature. For example, WAM was negatively correlated with CT max at 12°C but positively correlated at 28°C. Additionally, glucose substrate supported higher CaM than fatty acid, and fatty acid supported higher CaM than lactate, ketones and alcohol (LKA) or endogenous. However, these responses were highly variable with some individuals using much more FA than glucose. These findings suggest interindividual variation in physiological responses to temperature acclimation and indicate that additional research investigating interindividual may be relevant for global climate change responses in many species.« less