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Lecture 8 Methods Slides F09

Lecture 8 Methods Slides F09 - Lecture 8 Psychobiology...

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Unformatted text preview: Lecture 8 Psychobiology Methods Methods differ based on the experimental Methods differ based on the experimental subjects Preclinical Research: animals Clinical Research: humans Preclinical Preclinical Research Neurochemistry Neurochemistry: methods depend on Neurochemistry: 1. Substance measured ­ DNA, RNA, protein, small molecules (e.g. neurotransmitters), etc. 1. Nature of sample: tissue homogenates, tissue slices, fluid 1. Type of experiment: Ex vivo, In vivo, In vitro DNA: differs between subjects, not tissues DNA: differs between subjects, not tissues Polymerase Chain Reaction Gel Electrophoresis RNA: how much versus where RNA: how much versus where Reverse Transcription PCR In Situ Hybridization Protein: how much versus where Protein: how much versus where Western Assay Immunohistochemistry Receptor Binding Autoradiography Small molecules: e.g. neurotransmitters Small molecules: e.g. neurotransmitters HPLC Immunohistochemistry Neuropharmacology: Activation and Inhibition Neuropharmacology: of particular brain systems Anatomical Localization • Pharmacology • Lesions • Electrophysiology Central Drug Administration – When the goal of drug research is scientific applications (preclinical), drugs can be directly injected into the nervous system. – Intracerebral administration: Administration of a substance directly into the brain. – Intracerebroventricular (ICV) administration: Administration of a substance into one of the cerebral ventricles. Brain Lesions – Electrolytic lesion: A brain lesion produced electrical damage. – Aspirative lesion: A brain lesion produced by simply removing the tissue. – 6­hydroxydopamine (6­OHDA): A chemical that is selectively destroys noradrenergic or dopaminergic neurons. – Excitotoxic lesion: A chemical lesion produced by IC injection of an excitatory amino acid, that selectively kills neurons. – Sham lesion: A “placebo” procedure that duplicates all of the steps of lesion technique. Surgical Methods – Stereotaxic Surgery: Brain surgery using a stereotaxic apparatus to position an electrode or cannula in a specified position of the brain. – Stereotaxic atlas: A collection of drawings of sections of the brain of a particular animal with measurements that provide coordinates for the stereotaxic surgery. – Stereotaxic apparatus: A device that permits a surgeon to position an electrode of cannula into a specific part of the brain. In vivo Neurochemistry: Measuring chemicals in living and/or behaving animals – In vivo microdialysis: Allows sampling of extracellular fluid from a particular tissue or brain region that is measured with some other method (like HPLC). – In vivo voltammetry: Measurement by direct chemical reaction in the brain. – Brain scanning: Techniques used in humans can also be used in animals such as PET and fMRI. Anatomy Brain Anatomy – Sectioning: the brain is cut into thin slices and placed on slides for histological analysis – Fixative: A chemical such as formalin that preserves tissue. – Perfusion: Using the circulatory system to send fixative to the entire body. – Cryostat/Microtome: Instruments that produce very thin slices of body tissue. Cresyl Violet Section Cryostat Microtome Tracing Anatomical Connections – Anterograde labeling method: labels the axons and terminals of neurons whose cell bodies are located in a particular region. – PHLA­L: Phaseolus vulgaris leukoagglutinin; an anterograde tracer; taken up by dendrites and cell bodies and carried to the ends the axons. – Retrograde labeling method: labels cell bodies that give rise to the terminals that form synapses with cells in a particular region. – Fluorogold: A dye that serves as a retrograde label; taken up by the terminals and carried back to the cell bodies. Electrophysiology Electrophysiology – Macroelectrode: An large diameter electrode, usually metal. – Microelectrode: A very fine electrode, made from pulled glass tubes, used to record activity of individual neurons. – Single unit recording: Recording of the electrical activity of a single neuron. – Extracellular recording: Records electrical activity just adjacent to a cell. – Multiple unit recording: Records electrical activity from a larger region, containing several cells. – Electroencephalogram (EEG): An electrical brain potential recorded by placing electrodes on or in the scalp; measures the collective activity of large regions. Brain Stimulation: In addition to recording, brain areas can also be stimulated Stimulating Neural Activity – Multibarreled micropipette: A group of micropipettes used to infuse several different substance by means of iontophoresis while recording from a single neuron. – Microiontophoresis: electrical ejection of a chemical from a micropipette. Chemical markers of neural activity – cFos: A protein produced when a cell is active. Light activation of cells in the suprachiasmatic nucleus. Behavior Clinical Research Human Studies are far more limited: • Pharmacology – limited to approved drugs, and peripheral administration. • Lesions – only fortuitous, including lesions in attempted treatments. • Electrophysiology – only EEG except during surgery. • Behavior – Advantage (and disadvantage) of being able to ask patients questions. Brain Scanning Techniques Brain Scanning Techniques – Structural: early techniques, CAT scan (computerized axial tomography), superceded by structural MRI (magnetic resonance imaging) – Functional: – Positron emission tomography (PET): A device that reveals the localization of a radioactive tracer in a living brain. A modification of the MRI procedure that permits the measurement of regional metabolism in the brain. – Functional MRI (fMRI): PET Scan PET Scan ...
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