Animal experimental methods Flashcards
(21 cards)
Name four types of model systems.
- Immortalised cell lines
- Primary cells
- Isolated organs
- Intact organisms
What is “3R” ?
3R is a guiding principle for more ethical use of animals in testing.
Name the three points of 3R.
- Replacement: Use of methods which replace the use of animals in research
- Reduction: Use of methods that enable researchers to obtain more information from fewer animals
- Refinement: Use of methods that minimise potential pain, suffering or distress and enhance animal welfare for the animals used
What is stereotaxic surgery ?
- Precise surgical technique used to target specific areas in the brain
- It involves using a 3D coordinate system and a special frame to position the instuments precisely
- E.g. in mice their heads are fixed in this frame
What is stereotaxic surgery used for in animal experiments ? Name three examples.
- Inject drugs or chemicals directly into specific brain areas
- Implant electrodes for recording brain activity
- Create lesions to study brain function
Which three types of cannulas are used for microinjections ?
- Guide cannula
- Internal cannula
- Dummy cannula
What is the function of the guide cannula in microinjections ?
- Implanted into the brain to guide the internal cannula to the target area
- It stays in place during the whole experiment
What is the function of the internal cannula in microinjections ?
- It fits inside the guide cannula
- It delivers the drug or substance directly into the brain tissue
What is the function of the dummy cannula in microinjections ?
- It is placed inside the guide cannula when not in use (like a plug)
- It keeps the guide cannula clean and prevent blockage or infection
Name three advantages of microdialysis.
- Possible in awake animals
- Only little trauma
- Samples can be taken very frequently
Which methods are usually used to analyse the samples taken from microdialysis ?
- High performance liquid chromatography (HPLC)
- Immunoassays
How is microdialysis working ?
- A small probe with a semipermeable membrane is inserted into the brain area
- Fluid flows through the probe, allowing small molecules to pass through the membrane and be collected for analysis
What is the aim of microdialysis ?
- Measurement of chemical substances in the extracellular fluid of tissues, especially the brain
- Monitoring real-time chemical changes in living tissue
What is in-vivo fiber photometry ?
- Technique used to measure real-time neural activity in living animals
- Measurements via an optical fiber
- Initially used to report calcium dynamics
How does in-vivo fiber photometry work ?
- Genetically encoded sensors (like GCaMP) are introduced into specific brain cells via adeno associated virus (AAV)
- These sensors emit fluorescence in response to changes in calcium levels, which reflect neuronal activity
- An optical fiber is implanted into the brain region of interest
- Light is sent through the fiber to excite the sensors, and the emitted fluorescence is collected through the same fiber
- Changes in fluorescence intensity are recorded and analyzed to infer neuronal activity
What is the technique of choice to measure neurotransmitter dynamics in-vivo in rodents ?
In-vivo fiber photometry
What is the DREADD-system ?
Designer Receptor Exclusively Activated by Designer Drugs
-> Receptors which can only become activated by a synthetic substance
How does the DREADD-system work ?
- Modified receptors (DREADDs), which are not responding to natural neurotransmitters, are genetically introduced into specific neurons
- A designer drug is given to the animal and specifically effects the DREADD receptors without affecting other cells
- The effected receptors lead to changes in the activity of the targeted neurons
What is the DREADD-system used for ?
- Control of the activity of specific neurons in living animals
- Studying the function of specific brain circuits
- Investigating diseases like anxiety, addiction, or Parkinson’s
What is optogenetics ?
Optogenetics is a technique that uses light to control the activity of specific neurons in the brain.
How does the optogenetics work ?
- Light-sensitive proteins are genetically introduced into target neurons
- These proteins act as channel-switches that open or close in response to light, regulating the flow of ions and therefore the neuron’s activity
- Light is delivered through a optic fiber implanted in the brain
- This precisely activates or silences neurons in real time
