Nikes and Neurons Flashcards

Question

IN SITU HYBRIDIZATION Summary

Answer 1

control rat brain vs. rats that exercised for 7 days CA1, DG

Answer 2

The process of generating functional neurons from progenitor cells Progenitor cells proliferate and mature into functional neurons – integrate into neural circuits

Answer 3

Mark proliferating cells Bromodeoxyuridine (BrdU) • Synthetic thymidine analogue

Answer 4

Exposure to a rich environment induces structural & functional changes in the rodent brain and significantly increases hippocampal neurogenesis THEY TESTED the contribution of learning (via water maze) and physical activity (running wheel) on the generation of new dentate granule cells WHAT THEY DID: Divided the mice into 4 living conditions: 1. Enriched-environment (aka: enriched) 2. Hidden-platform water-maze learning (aka: swimmer & forced exercise) 3. Voluntary exercise (aka: runners) 4. Standard living (aka: control) Injected with BrdU for the first 12 days & examined the number of BrdU+ cells in the dentate gyrus ASSESSMENT OF SUBGRANULAR PROGENITOR CELL PROLIFERATION

Answer 5

Larger housing area More friends to interact with Greater opportunity for physical activity Greater opportunity for learning

Answer 6

IS LEARNING IN THE MORRIS WATER MAZE ASSOCIATED WITH CELL PROLIFERATION? ASSESSED PROLIFERATION BY MEASURING BRDU INCORPORATION

Answer 7

Runners were the only ones to be significantly better

Answer 8

Runners were significantly the best. Enriched Environment mice were also significantly affected. Everybody else was not much different than the controls.

Answer 9

Are they functional? YES! Running enhances neurogenesis, learning, and long-term potentiation

Answer 10

....This was known... but Does physical activity affect synaptic plasticity & learning?

Answer 11

THEY TESTED If exercise will increase synaptic plasticity, learning, and neurogenesis WHAT THEY DID: Running wheel vs. controls with no wheel for excursive

Answer 12

Remember how I said reviewers can be Pains? • “Scientists, researchers and animal rights advocates have argued over the years about the nature of mice running on wheels in their cages. Rights activists claim the running is a form or neurotic behavior brought about by living in the confines of a small cage. Some researchers, on the other hand, have suggested that the mice seemed to like, or enjoy running on the wheel, and even exhibited unhappy behavior if a wheel was removed.” “To learn more, Meijer & Robbers decided to carry out a very simple experiment—they set up a running wheel in their backyard, then used an infrared camera to capture on tape how animals in the wild would respond.”

Answer 13

And, to personify mice, maybe even enjoyed by mice

Answer 14

``` Training • 2 or 4 trails / day • 6 days • Subject placed in pool near edge • Entry point varied • Each trial last 40s or until the mouse found the platform ``` Testing was done between day 30 and 49 Length of swim path (path) & time to reach the platform (latency) were recorded TWO TRIAL/DAY Slight, but significant improvements in • Path length (runner

Answer 15

Running does not affect initial EPSP amplitude BUT Running increased EPSP amplitude at a greater rate

Answer 16

LTP IN THE DG AND THE CA1 SCHAFFER COLLATERAL IS USUALLY MEDIATED BY NMDA RECEPTORS

Answer 17

LTP induction was completely blocked. Suggests that NMDA receptors mediate running induced increases in LTP

Answer 18

BDNF is an exercise-induced trophic factor Wheel running increased LTP in the dentate gyrus Even slugs will use a running wheel

Answer 19

THIS PAPER IS NOT LOOKING AT THE EFFECT OF EXERCISE FOR THE SAKE OF EXERCISE… its not neurons, its about oligodendrocytes…

Answer 20

WRAP NEURONAL PROCESSES IN MYELIN a glial cell concerned with the production of myelin in the central nervous system.

Answer 21

protein and phospholipids that form an insulating sheath around axons increases the speed of electrical communication between neurons white matter (myelin tracts) vs grey matter (neurons) in the CNS, myelin is made by oligodendrocytes

Answer 22

majority are born and develop in the first 6 weeks (in rodents) there is some oligo proliferation in the adult mice oligo precursor cells are called NG2+ glia • NG2 is marker (a protein that can be immunostained and observed) NG2+ glia are found in the adult brain

Answer 23

YES MRI studies on piano players (or other people who learn complex motor tasks) show structural changes in white matter If you train rodents in new motor learning tasks, you can find changes to the structure of their white matter UR: unskilled reaching SR: skilled reaching

Answer 24

HOW DO THEY ANSWER THIS QUESTION? Use Cre-LoxP conditional deletion techniques, they target a gene (myelin regulatory factor, Myrf) that when lost, blocks the maturation of oligodendrocytes and thus myelinating capability of new oligos * Majority of oligos are already formed * This approach only inhibiting the ability of new oligos to myelinate * Use the Pdfra promoter (active in NG2+ oligo precursor cells) to drive Cre-ERt2 expression * ER-T2 = estrogen receptor – treat with tamoxifen and Cre translocates from membrane to the nucleus where it can act on LoxP sites * Spatial control conferred by the Pdfra promoter * Temporal control conferred by ER-T2 (no deletion until tamoxifen treatment)

Answer 25

1. Deleted Myrf 2. Waited 5 weeks 3. Then asked: does loss of oligo precursor cells cause demyelination? 4. Stained for myelin (dark blue/purple) 5. Found no difference in gross myelin characteristics 6. Looked a myelin wrapping by EM and found no difference

Answer 26

...rotarod

Answer 27

Deletes Myrf from both oligo and oligo precursors Sox10 – drives Cre expression in oligo precursor & mature oligodendrocytes --> lose myelinating ability in both

Answer 28

Now, what about the motor learning task? Complex Wheel Running (CW) • This running wheel has missing rungs • Mice love running, so missing rungs will not stop them, they will ‘learn’ to deal with the missing rungs ``` THE EXPERIMENT... Cre active = Myrf loss of function in oligo precursor cells 3 weeks after Myrf Loss-Of-Function in OPs introduced to complex wheel ``` MYRF-/- MICE RUN SLOWER

Answer 29

Someone was not convinced… Repeated the experiment a total of 5Xs N=36 Myrf+/- N=32 Myrf-/- So do mice need active remyelination to remember how to use the complex wheel? No!!

Answer 30

CC1 = marks mature oligos EdU = marks proliferating cells • similar to BrdU but easier to use

Answer 31

a synthetic nucleoside that is an analog of thymidine. BrdU is commonly used in the detection of proliferating cells in living tissues. BrdU can be incorporated into the newly synthesized DNA of replicating cells (during the cell cycle in which DNA is replicated), substituting for thymidine during DNA replication. Antibodies specific for BrdU can then be used to detect the incorporated chemical (see immunohistochemistry), thus indicating cells that were actively replicating their DNA. Binding of the antibody requires denaturation of the DNA, usually by exposing the cells to acid or heat. BrdU can be passed to daughter cells upon replication. BrdU has been demonstrated to be detectable over two years post-infusion.

Answer 32

Spike in precursors 2 days later spike in oligos

Answer 33

Novelty of learning how to run on the CW is what triggered oligogenesis and myelination

Answer 34

Suggests new oligos are important for motor skill learning/acquisition of new tasks • How? • New connections are formed and/or existing connections are strengthened which stimulates myelination or myelin remodeling Is there other evidence for this? • Learn a new language = new myelination

Answer 35

New myelination / new oligos are necessary for motor learning Existing myelination is sufficient to maintain previously learned motor tasks

Answer 36

Learning a new motor skill (such as juggling) alters the structure of the brain’s white matter, which contains many OLs, suggesting that late-born OLs might contribute to motor learning. Consistent with this idea, we show that production of newly formed OLs is briefly accelerated in mice that learn a new skill (running on a “complex wheel” with irregularly spaced rungs).

Answer 37

This prevented the mice from mastering the complex wheel. Thus, generation of new OLs and myelin is important for learning motor skills.

Answer 38

(MRI) has detected changes in the structure of white matter in people trained in complex sensorimotor tasks such as playing the piano, juggling, or abacus use.

Answer 39

Preventing new OL production does not trigger demyelination

Answer 40

a transcription factor required in OLs to initiate & maintain their myelination program It is not expressed in OL precursors, in other CNS cells, or in Schwann cells, which myelinate PNS axons

Answer 41

We refer to the tamoxifen-treated mice as P-Myrf (+/−) and P-Myrf (−/−). Recombination at the Myrf locus was confirmed by reverse transcription polymerase chain reaction.

Answer 42

our strategy prevents the formation of new OLs without affecting preexisting OLs

Answer 43

In contrast, S10-Myrf (−/−) mice developed severe tremors around 1 month posttamoxifen, and their performance on the rotarod was seriously impaired, similar to when Myrf deletion was targeted to mature OLs using Plp-CreER.

Answer 44

Active myelination is not required to recall a prelearned skill