Chapter 4: Methods of Research Flashcards
What is an example of tests with high/low face validity?
H: blood pressure (tests that closely resemble those in humans)
L: human brain conditions; delusions, altered mood, emotions (do not resemble those in humans)
What are the outcomes scientists are looking for during animals testing?
- have a predictive validity
- sensitive; show a dose-response relationship
- high reliability (same result every time)
- specification; for that particular drug or class being screened
- demonstrate the same rank order of potency
Purpose for the paradigm for analgesia:
- measurement of pain
2. evaluate pain reductions by drugs without loss of consciousness
What is the test utilized in the paradigm for analgesia?
Tail-Flick test
What is the T-F test?
- purpose
- measurement
- conclusion
- a measurement of animal response to pain (heat applied to the tail)
- time between the onset of the stimulus and when the animal removes its tail away from the heat source
- the less pain perception, the longer animals will keep their tail close to the heat source
Purpose for the paradigm for motor function:
measure motor or locomotor activity
What is the task assignment for the motor function paradigm?
open-field test
The effect of drugs on motor function:
impaired locomotion and catalepsy (full rigidity of the body)
Purpose for the paradigm for reward-seeking behavior:
- reward and addiction
2. learning and memory
What is the task assignment for the reward-seeking behavior (L&M)?
operant or instrumental conditioning
Once behavior is learned, the requirements for reinforcement can be altered according to a schedule. What are these variants?
based on ratios or time intervals
- fixed-ratio (FR)
- fixed-interval (FI)
What is the meaning of aversive reinforcers? What is
an example of variants with aversive reinforces?
increased probability of a response that terminates an aversive condition
animal is trained to turn off an electrical shock by pressing the lever
To test reward-seeking behavior of addiction what type of paradigm is used?
self administration
How is the assessment of cognitive function achieved in animals?
evaluation can be done by creating situations for decision making and temporarily holding information
What paradigms are used for the assessment of higher-order cognitive processes of decision making?
T-Maze of Y-Maze
Spatial learning:
learning to navigate your environment
What paradigms are used for spatial learning?
- Morris Water Maze
2. 8-Arm Radial Arm Maze
What happens during the Morris Water Maze?
involves a circular water pool where animals must swim until they find a platform hidden just a couple of cm below the surface
How does spatial learning play a role in the Morris Water Maze?
animals learn the spatial position of the platform relative to visual landmarks in the test room
How does spatial learning play a role in the 8-Arm Radial Arm Maze?
animals need to learn that food is available in alternating arms or a few arms
What paradigms are used for working memory?
Delayed-Response test
What kind of paradigms are based on innate traits?
those that test anxiety
**behavioral phenotypes of anxiety come hard-wired in the brain
List the paradigms used for evaluating anxiety:
- Light-Dark Crossing Task
- Open-Field Test
- Elevated-Plus Maze
Light-Dark Crossing Task measures…
time spent on dark versus lit up compartments
number of crossings
Light-Dark Crossing Task conclusion…
the more rodents spent in (or faster they cross to) the lit-up compartment, the less anxious they are
Open-Field Test (evaluating anxiety) measures…
time spent on periphery versus center
number of crossings through the center
Open-Field Test (evaluating anxiety) conclusions…
the more time rodents pent in the center, the less anxious they are
What are some antianxiety drugs? How would they effect the outcome of an OFT?
- Buspiridone (Buspar)
- Alprazolam (Xanax)
- Clonazepam (Klonopin)
- Diazepam (Valium)
- Lorazepam (Ativan)
these drugs should increase the time spent at the center of the OFT
Elevated-Plus Maze measures…
time spent on closed arms versus opened arms
number of entries into arms
Elevated-Plus Maze conclusions…
the more time rodents spent in the open arms, the less anxious they are
What are the two paradigms for social interaction?
- One-Chamber Social Interaction Tests
2. Three-Chamber Social Interaction Tests
What occurs during the OCSI test?
two rats are place in a cage where neither has established territory and slowly conditions are introduced
OCSI test conclusions…
normal interactions decrease when conditions are introduced
**bright light, increase anxiety, drugs
How is the OCSI relevant to humans?
relevance to disorders characterized by poor social interaction such as ASD (autism spectrum disorders)
Paradigm used for fear:
Pavlovian or Classical Fear Conditioning
Conditioned emotional responses are based on […].
associative learning
Paradigms for depression:
- Forced Swim Test (FST)
2. Tail Suspension Test
Conclusion for paradigms for depression…
the faster they give up the struggle, the more “depressed” they are (“lower mood”)
List the medications that allow the time interval to increase in the depression paradigms:
SSRI
- Prozac (fluoxetine)
- Paxil (paroxetine)
- Zoloft (sertraline)
In the fear paradigms, the cues became…
predictor of an aversive effect
How do we examine the brain?
stereotaxic surgery
What are the benefits of stereotaxic surgery?
- precise implantation
- devices explore patterns of neural activity
- manipulate function
- direct infusion of drugs
How are brain examinations precise in targeting defined regions of the brain?
3D coordinates provide a brain atlas
What are the 2 techniques of brain lesions?
- electrolytic lesions
2. chemical lesions
Which brain lesion was a popular technique in the past?
both
Describe electrolytic lesion process:
unipolar electrodes could be inserted into specific brain regions to deliver electrical currents high enough to damage cell/tissues in the area
What is the result of the lesions?
comparing before and after lesion gives information of the functions in that particular brain region
What happened when electrolytic lesions were made to the basal amygdala (BA) of rodents?
there was difficulty learning about threats; couldn’t associate auditory cure paired with electrical shocks
What is the difference in the process of a chemical lesion vs an electrolytic lesion
chemical uses specific neurotoxins that damage the brain tissue
Where are neurotoxins of chemical lesions injected? How?
small amount is injected to a specific region using a cannula (piece of fine metal tubing)
Cannulas administer…
neurotoxins as well as drugs (whether agonist or antagonist)
What is an example of a chemical lesion done on rodents (area and effect)?
dorsal hippocampus (dHPC)
rodents had trouble learning contextual features of the environment (could specify locations with food)
What are the methods used to measure NT release?
- microdialysis
2. voltammetry
Microdialysis is a technique used to measure […] content from the […].
NT; extracellular content
Microdialysis advantage:
examine NT release in particular brain regions while animal is actively engaged in specific behaviors
Explain the process of microdialysis:
retrieval of a small amount of NT/extracellular content is done through a cannula
cannula has specialized semipermeable membrane
volume collected analyzed through HPLC use that separates based on molecular size or ionic charge
Voltammetry is a technique used to measure […] content from the […].
NT release; use of electrodes
Explain the process of voltammetry:
electrodes are implanted using stereotaxic surgical techniques
applied voltage causes changes in current flow (measured)
Voltammetry advantage:
measurements can be made continuously as animals perform behavioral tasks
Voltammetry is most often used to measure…
dopamine NT release
What is the classical method to stimulate brain activity?
electrical stimulation
Explain electrical stimulation:
bipolar electrodes are implanted and small electrical pulses at high frequencies can be delivered
pulses generate neuronal AP and NT release
Electrical stimulation should produces effects similar to those…
- seen during endogenous NT release
2. during application of agonists
Stim electrodes can be used as […] for neural stimulation in humans.
treatment
What conditions can be treated through stim electrodes?
- tremor control in Parkinson’s pt
2. unretractable OCD
What are the methods for recording neural activity?
- single unit recordings
- local-field potentials
- intracellular recordings (path clamp electrophysiology)
What does the SU record?
extracellular fluctuations in voltage generated from nearby individual neurons
What questions can be answered utilizing the SU record system?
What are the firing patterns of individual neurons in a given brain region during particular behavior or during drug administration?
What does the Local-Field Potential record? What does this result in?
extracellular levels in voltage fluctuations for an entire brain region
summation allows examination of oscillatory patterns**
**(beta/theta/gamma)
Oscillatory patterns and what they might show:
gamma = problem solving and concentration
beta = busy, active mind
alpha = reflective, restful
theta = drowsiness
delta = sleep, dreaming
In which type of neural recording must animals be anesthetized?
intracellular recordings
How can pieces of brain tissue be kept alive?
using artificial CSF
What does the Intracellular method record?
electrical records of ion channel time patterns
when it opens/closes/ion flow
Method of tissue extract for the following target molecules:
- receptor site
- receptors and other proteins
- mRNA
- radioligand binding
- radioimmunoassay (RIA); western blot; ELISA
- dot blot; northern blot
Radioligand Binding:
- preformed in brain tissue slices
- requires incubation of tissue homogenate with radioactively labeled ligands
- amount of radioligand bound to the tissue is measured with a gamma counter
- amount of bound radioligands serves as a measure of receptor density in the tissue
- pictures taken for visualization are called “receptor of molecule autoradiographies”
Immunocytochemistry:
- brain slices are fixed and incubated with an antibody
- antibody attaches to the antigen wherever cells that contain that antigen are present
- antibodies are tagged using secondary antibodies that carry colored dyes or fluorescent proteins
Enzyme-linked immunosorbent assay (ELISA):
- antibodies are linked to an enzyme that acts on a substrate to form a colored product
- color intensity is proportional to the amount of antigen present
In situ hybridization (ISH):
- visualize cells in tissue slices that are manufacturing a particular protein
- detects the specific mRNA molecules that direct synthesis of proteins essential to neuron function
- amount of mRNA gives an estimate of rate of protein synthesis
- ISH technique depends on the creation of probes by labeling single-stranded RNA fragments with base-pair sequences complementary to the mRNA of interest
- RNA probes are labeled with radioisotopes or dyes
Northern blod/dot blot:
- ISH using a tissue homogenate rather than a tissue slice
2. measures amount of mRNA rather than visualizing its location
What are the techniques to brain imaging in humans?
- 2-DG
- CT Scan
- PET
- MRI
What does a 2-DG technique indicate?
which brain regions are most active (after drug technique)
How is the 2-DG able to see the activity?
nerve cell firing will increase, metabolic rate increases, utilization of glucose/O2 increases
2-DG stands for
2- Deoxyglucose Autoradiography
Computerized tomography is also known as…
CAT scan or CT scan
What does a CT scan do?
increases the resolution of X-ray images and makes 3D images
How does a CT scan accomplish imagining?
cylindrical CT scanner rotates around the head sending narrow/parallel x-ray beams through the tissue to be detected on the opposite side
What does a PET scan do?
- determines locations of radioactively labeled drugs
- located areas of brain activity (blood flow, glucose, or O2 utilization) when person is performing certain tasks or problem solving
What does a MRI do?
3D imaging, functional MRI combines anatomical MRI images with functional activation of distinct parts of the brain based on changes in blood oxygen levels
What does a MRS do?
uses MRI data to calculate concentration of brain chemicals and evaluate metabolic changes
What are some of the specific molecules that can be found in magnetic resonance spectroscopy?
- glutamate
- choline
- NT metabolites
What is phMRI? What does it do?
- pharmacological MRI
2. analyzes changes in brain function following drug administration, location, and time course of drug action
How is phMRI useful?
predicts response of patient by screening brain function especially for: high risk, high cost treatment, those that take months to show effectiveness
Gene knockouts/knockins:
DNA is altered; foreign gene is added to that DNA
Knock-Out Mouse Models:
lack a gene for making a particular protein
Knock-In (KI) Mouse Models:
inserted gene is modified to produce slightly different protein, often by one AA
KI allows the study of relationship between…
protein structure and function
KO allows the study of relationship between…
function of the deleted gene
KI in neuropharmacology the protein of interest is often…
receptor subtype or an enzyme
CRISPR technique stands for…
cluster regularly interspaced short palindromic repeat
What is the CRISPR technique? What is the Guide RNA? What is Cas9?
faster way to genetically engineer mice
identifies a specific genomic sequence to be modified
a nuclease that cuts out the specified section
Transgenic Mouse Models:
one gene is substituted for another
human genes can be inserted to produce models for mental diseases
Potential problems with transgenic mice:
- behaviors are controlled by multiple genes (change/elimination alters only a small part of the overall behavioral trait)
- compensation by other genes for the missing or over-expressed gene may mask effect of the mutation
What are some modern methods to help manipulate nerual activity?
- optogenetics
- chemogenetics
- magnetogenetics
What are the approaches of optogenetics?
- uses light to exert temporally and spatially precise control over the functioning of genetically altered population or neurons or neural pathways
- neurons/pathways can be artificially excited/inhibited almost instantly using microbial opsins
- opsins form membrane-bound channels that allow the passage of ions (Na to stimulate; Cl to inhibit)
Example of Opsins:
- ChR2 forms cation channels permeable to Na ions
- Halorhodsopin is a Cl- ion pump
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