Lecture 4 Flashcards
Advantages of using rats for neuroscience
- Cheap housing/maintenance/breeding
- Friendly disposition and easy to train
- Intelligent and agile
- Resistant to infection
- Many inbred strains available
Neuroscience manipulation techniques
- Lesions: mechanical, chemical, electrolysis
- Electrical stimulation (excite or inhibit neural function)
- Pharmacological: injection, osmotic pumps, microdialysis
- Genetic manipulation
- Behavioural manipulation
Neuroscience monitoring techniques
- In vivo:
1. Electrophysiology
2. Microdialysis
3. Behavioural evaluation
Ex vivo:
1. Localization of tissue components: Histology, Immunohistochemistry, Hybridization for mRNA or DNA
2. Quantification of components in tissue homogenates
Stereotaxic surgery
Microinjections
Lesions
Cannula placement
Microdialysis
Electrodes
Headsets
Are all used in stereotaxic surgery
Microdialysis
A catheter is injected into or near to the cell which acts as a blood capillary. Extracellular substances diffuse accross the membrane of the catheter into the perfusion liquid inside the catheter.
Substances inside the catheter can also flow out.
The absolute recovery of a substance depends on the size of the pores of the membrane, length of the membrane, flow rate of the perfusion fluid and the diffusion coefficient of the compound.
Microdialysis applications
- Continuous monitoring of chemical events in living tissue
- Continuous drug delivery
- Contemporaneous drug delivery and monitoring of drug effects
Levels of electrophysiology
- Single ion channel
- Single unit (cell)
- Multi unit
- Field potentials
- Brain potentials (ECG, EEG, MEG)
Patch clamp recording
Micro pipette clamps on to part of the cell body and can monitor a single ion channel and has very stable intracellular recording compared to conventional electrode recording
Intracellular recording
This measures the voltage across the membrane of the cell.
Sharp electrode penetrates cell membrane.
Has extracellular reference electrode in a bath
Extracellular recordings
- One cell
- Recording electrode close to the cell
- Commonly in vivo
- Reference electrode = ground
- Multi unit recording
Field potentials
Extracellular field potentials are local current sinks or sources that are generated by collective activity of many cells.
Two electrodes are implanted, one inside the cell and one outside. The intracellular one records change in membrane potential caused by influx of positive sodium ions. The extracellular electrode measures the outside getting more negative.
EEG
This measures correlated synaptic activity caused by post-synaptic potential of cortical neurons.
The ionic currents from action potentials don’t contribute much to EEG recording. Rather the extracellular ionic currents caused by dendritic electrical activity are what gives the signal.
Post-synaptic potentials give the signal.
Oscillations are synchronized activity over a network of neurons.
fMRI
- Based on blood oxygenation (Blood-oxygen-level-dependent imaging)
- Theory: increased flow of oxyhemoglobin-rich blood to ‘active’ brain
- Disadvantage: Does not measure neural activity directly. Can only measure changes in BOLD signal
- Advantage: can measure subcortical structures
Genetic engineering
The proteins occuring in an organism are altered by altering the DNA.
The transgene
A piece of foreign DNA carried by a transgenic organism.
Either the foreign DNA exists in the cell in the form of a plasmid (prokaryote) or the foreign DNA is integrated into the host genome (mammals)
