5 - neuroplasticity Flashcards by Angelica J

what is neuroplasticity

brain’s ability to reorganize and restructure itself

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what are 3 main things associated with neuroplasticity / what happens

formation/death of neurons
formation/loss of new neuronal connections
strengthening/weakening of existing connections

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what do drugs do to memory and why

decrease in neurogenesis is linked to memory issues

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what are dendritic spines

dendritic arms covered in spiny extensions

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what can cause dendritic arms to change shape

learning, stress, drugs

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whats the role of dendritic spines in the nucleus accumbens

this is where synaptic contacts are made with other neurons (medium spiny neurons)

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where are most dendritic spines

where there are lots of glu receptors (responding to various components of reward pathway)
-but they can be in many brain regions

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what happens in dendritic spines

major site of mostly excitatory input from other neurons, mostly from PFC, also hippocampus and amygdala

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what receptor types do dendritic spines have

for glutamate

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what causes the change and shape and density of dendritic spines (what allows it to do this)

actin rearrangement

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where are the glu receptors on dendritic spines

the tip of projections

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what flows through activated glu receptors in dendritic spines

calcium

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what does calcium flow through activated glu receptors cause

actin structure to change

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what happens when glu activates their receptor in the dendritic spine

calcium pores open to enter, actin changes shape

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what do drugs do to the dendritic spine genes

modulate genes for the cytoskeleton

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what do opiates do to dendrites in the NAc

decrease spines and number of dendrites

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what do opiates do to dendrites in the VTA

decrease cell body size

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what do stimulants do to dendritic spines

increase growth

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what do stimulants do to dendrites in the NAc

increase number of dendrites and the density and size of of the spines

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what do stimulants do to dendrites in the VTA

increase density and size of spines

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which part of brain gets increased or decreased number of dendrites due to drugs

the NAc

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what is thought to cause the basis for experience-dependent learning and memory

synaptic plasticity of dendritic spines

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what does glu do in memory related processes

plays a critical role in mediating memory related processes

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where are most of the dendritic spines found

on MSN in nucleus accumbens

Also VTA, hippo & amyg

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what happens to AMPA and NMDA receptors with cocaine exposure

increase AMPA receptor and AMPA:NDMA ratio

what happens when AMPA receptors are activated by glu

increase entry of calcium

what is long-term potentiation

a persistent strengthening of synapses based on recent patterns of activity -lasting potentiation of excitatory synaptic transmission

what does increased calcium entry into dendritic spines do

trigger structural changes

what is important with long-term potentiation (what is it a hallmark of)

learning

what are the types of dendritic spiny DA releasing neurons

type 1 is affected by glu (grows more spines) | type 2 not affected

what happens when type 1 DA releasing neurons are exposed to cocaine

increase glu receptors

what happens with increase glu receptors (what does this cause)

more potential for excitatory input from other neurons

what happens when type 2 DA releasing neurons are exposed to cocaine

nothing

where are these type 1 and type 2 receptors

ventral tegmental area (in rats)

even with drug use extinction, can you reinstate drug seeking behaviour? how? how fast do you see brain changes?

yes, things like flashing a light (if that was associated to drug taking) can elevate AMPA/NMDA ratio within 15 mins

what happens when you lesion glu projections from PFC to nucleus accumbens

there is no glu signal or input, no drug reinstating behaviours can happen

can anticipation affect dendritic spines

yes, it can increase the size and stuff

what causes over-leaning in dendritic spines

strengthening of pathways by glu

what stimulates BDNF production

calcium influx

what do stimulants do to BDNF levels

increase, even during abstinence

what does high BDNF levels do

more spines and increased cell body size

what does morphine do to BDNF levels

reduce

what does low BDNF levels do

fewer spines, less AMPA receptors

what does BDNF do to ERK

affects its pathway

what are some main roles of the ERK pathway

affect genes that code for cytoskeleton proteins involved in spine formation

where is the growth of new neurons essential for psychiatric issues and deciphering between cues that signal pleasant or unpleasant experiences

hippocampus

what 4 things can inhibit neurogenesis

corticosteroids (stress hormones) anxiety depression addiction

what 4 things can stimulate neurogenesis

enriched environment exercise antidepressions electroconvulsive shock therapy

what are the main areas of neuronal growth

subventricular zone olfactory bulb subgranular layer of the hippocampus dentate gyrus

does the subventricular zone alter neurogenesis in response to drugs

does the olfactory bulb alter neurogenesis in response to drugs

does the subgranular layer of the hippocampus dentate gyrus alter neurogenesis in response to drugs

yes!

what is a lab technique used to measure new neuronal growth

brdU (mimics thymidine) that only interact with DNA when replicating, antibody to brdU will produce a signal when cells contiain brdU in their DNA

where do progenitor cells arise

subgranular zone in the hippocampus

what happens in the granular cell layer

cells born from the subgranular zone migrate and mature here - establish neuronal connections

where is the subgranular zone and the granular cell layer

subgranular zone is beneath the granular cell layer

what does chronic cocaine do to BrdU incorporation

decrease (decreased proliferation)

what is proliferation

formation of new neurons

what does acute cocaine do to BrdU incorporation

single exposure has similar results but it recovers after a few days

what does binge ecstasy do to brain (neurogenesis)

doesnt decrease neurogenesis but kills new neurons

what does methamphetamine do to brain (neurogenesis)

impairs both proliferatoin and survival

what does nicotine do to brain (neurogenesis)

impairs neurogenesis and certain types of memory

what does lack of sleep do to brain (neurogenesis)

decrease neurogenesis

what does chronic morphine do to brain (neurogenesis)

decrease neurogenesis (so its not the stimulants that do this, its the addictive nature of the drugs)

what 4 things are altered when neurogenesis is inhibited (rats, experimentally)

- self-administer more cocaine - take higher doses - work harder for more doses - harder to extinguish behvaiours

how are rates of addiction different with animals that have neurogenesis inhibited

more vulnerable to addiction

how did they inhibit neurogenesis in the experiment

X-ray irridation of hippocampus in rats

why is it harder to extinguish a behaviour if neurogenesis is inhibited

because extinguishing a behaviour is still a type of learning

what is contextual memory

associating place with events | memories triggered by smells, sights, taste... certain contexts

what part of the brain is associated with contextual memory

hippocampus (learning and memory centre)

what happens with contextual memory learning with drug use (hippocampus)

deficits in memory processing of drug-associated cues, enhancement of drug-reinforcement learning

how is glutamate affected with a lack of new hippocampus neurons in hippocampus

excessive glutamate release from HC onto PFC and NAc neurons in presence of drugs/cues

what happens with excessive glutamate release at PFC

loss of neuronal mass and dysfunction

what happens with excessive glutamate release at NAc

excessive stimulation, general dysfunction

what are 3 possible mechanisms for impaired neurogenesis

- drugs that activate DA receptors in hippocampus - drugs that cause oxidative stress (damage mitochondria in developing neurons) - influence levels of growth factors (BDNF, VEGF)

is CBD or THC active

THC

what does CBD do to neurons

increase neurogenesis, increase cell survival and maturation

what does THC do to neurons

reduce learning abilities (in mice) and no effect on neurogenesis

where can CB1 receptors be found

dentate gyrus