Neuroscience Techniques: Injections and Lesions

Systemic Injections

• Involves injecting a drug into the bloodstream, affecting the entire organism.
• Quick and simple method compared to others, suitable for broader research questions.
• Not ideal for studying specific neurological structures.
• Dosage is determined by animal weight (mg/kg) and drug's dose-response curve.
• Routes of administration include subcutaneous, intraperitoneal, and intravenous.

Lesions

• Permanent damage to targeted brain regions is created to study effects on behavior.
• Uses NMDA, which over-excites and kills neurons in selected areas.
• Histological analysis post-mortem is conducted to confirm the extent of lesions.
• Procedure involves stereotaxic surgery: anesthesia, skull landmark identification, drilling a hole, injecting drugs, and recovery period.

Infusions

• Involve stereotaxic surgery to implant a guide cannula above a specific brain target.
• Direct infusion of drugs into neural targets allows for precise effects without systemic influence.
• Histological confirmation of cannula placement is essential.
• GABA agonists can be used for inactivation, receptor agonists/antagonists for modulation.
• Provides temporary drug effects and is used in within-subject designs.

Designer Receptors Activated by Designer Drugs (DREADDs)

• Allow chemogenetic control of neuronal activation/inhibition in targeted regions.
• Involves viral vectors that contain DREADDs and fluorescent tags.
• Injection of CNO activates designer receptors, providing good temporal specificity.
• Targets specific cell types using genetic promoters or cre-recombinase techniques.
• Easier for extended testing compared to infusions, with verification of expression and target cell types post-mortem.

Optogenetics

• Enables control of neuronal activity through light stimulation.
• Viruses are injected for opsin expression, combined with an implanted optic fiber for light delivery.
• Key considerations include choice of virus (e.g., AAV serotypes), genetic promoter sequences, and opsin types (e.g., Channelrhodopsin for excitation, Halo-rhodopsin for silencing).
• Timing for effective virus expression ranges from 3 to 6 weeks.
• Cre-recombinase approaches allow selective targeting of certain cell types when necessary.
• Histological analysis post-mortem checks for expression locations and specific cell types.

Explore various neuroscience techniques including systemic injections, lesions, and infusions. Learn how these methods impact brain study and behavior research. This quiz covers dosage calculations, surgical methods, and targeted drug administration.