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Discussion of ways to manipulate neuronal activity through receptors
Types of receptors mentioned:
- Chemogenetic receptors (Designer Receptors Exclusively Activated by Designer Drugs - DREADs)
- Activation by CNO (clozapine N-oxide)
- Importance of DREADs in modulating circuit excitability
  - Useful for modulating the activity of entire structures like the hippocampus, amygdala, or frontal cortex
  - Administration methods: oral or injection, ensuring widespread receptor activation throughout the brain
- Optogenetic receptors
- Ion channels responding to specific light wavelengths
- Channelrhodopsin (blue light): opens sodium channels
- Halorhodopsin (yellow light): opens chloride channels
- Optogenetics useful for real-time measurements; focuses on specific brain regions
Comparison: Chemogenetics suitable for whole structures; optogenetics better for specific neuron activation and inhibition.

Chemogenetic effects more prolonged due to CNO's circulation
- Estimated half-life: approximately 24 hours, varying with administration method: direct injection vs. oral intake

SNARE Proteins:
- Present on presynaptic membrane and synaptic vesicles
- Types:
- V-SNAREs (vesicular SNAREs): including synaptotagmin
- T-SNAREs (target SNAREs): present on presynaptic membrane
- Function: V-SNAREs and T-SNAREs tether together to dock synaptotagmin which acts as a calcium sensor
- Calcium entry activates synaptotagmin, catalyzing synaptic vesicle fusion with the presynaptic membrane

Resting Membrane Potential: typically around -70 mV
Factors determining membrane potential:
- Membrane permeability to different ions;driving force affecting ion movement across the membrane
Equilibrium potential calculation: Nernst equation outlined as: $E<em>{ion} = \frac{RT}{zF} ext{ln} \frac{[ion]</em>{outside}}{[ion]_{inside}}$
- Various constants contributing:
- Gas constant (R)
- Faraday's constant (F)
- Temperature (in Kelvin)
Membrane permeability dictates flow, with driving force indicating each ion's movement potential
- Positive driving force indicates that cations exit and anions enter; negative driving force indicates that cations enter and anions exit
Example Calculation:
- Sodium driving force calculated at rest approximately -140.84 mV (indicating strong inward movement)
- Calcium: -201 mV driving force (greater polarization)
- Potassium: +18 mV driving force (indicating outward movement)

Plane Descriptions:
- Horizontal Plane: Viewed from above, front (rostral/anterior), back (caudal)
- Sagittal Section: Divides left and right hemispheres down the midline
- Coronal Section: Divides front from back, akin to a crown

Overview: Rare, severe encephalopathies associated with:
- Frequent seizures (epileptiform discharges)
- Intellectual disabilities and developmental delays
- MRI imaging techniques differentiate between T1 and T2 weighted images to highlight structural abnormalities
- T1 weighted: darker CSF, lighter white matter; T2 weighted: bright CSF, darker white matter
MRI Analysis: Identifying demyelination or inflammation; finding general cerebral atrophy with decreased cortical volume, particularly in the frontal lobe

Ion Channels Role: Crucial for action potential control and timing
Disruption in timing can lead to uncoordinated neuronal firing and hence seizures
Highlighted the importance of potassium channels in establishing resting potential and affecting repolarization during action potentials
- KV2.1 channel: significant delayed rectifier channel, encoded by KCNB1 gene
- Channel mutations can disrupt structure, selectivity, activation/inactivation times, leading to abnormal neuronal activity

Electrophysiology Definition: Method for inducing current in a cell and recording responses to assess ion channel behavior
Different techniques include:
- Cell-attached recording: Non-disruptive; measures whole neuron firing
- Whole-cell recording: Involves membrane disruption; continuous cytoplasmic measurement
- Inside-out and Outside-out Recording: Manipulating intracellular/extracellular environments while measuring ion flow
Kinetic Behaviors of Ion Channels:
- Activation: Opening in response to depolarization
- Deactivation: Closing in response to repolarization
- Inactivation: Channel ceases to conduct ions despite ligand presence; can occur in open or closed states

Temperature Effects: Increased temperature accelerates kinetics; can change equilibrium potentials (e.g. potassium during fever) despite inducing seizure susceptibility
Activation and Inactivation Dynamics:
- Slower activation increases early outward current but peak current is unaffected
- Delayed deactivation increases tail currents; sustained potassium conductance can disrupt timing and prolong neuron recovery

A rare KCNV1 mutation in a sibling pair leads to seizures resistant to standard antiepileptic treatments; the condition emphasizes the role of KV2.1 in neuronal excitability
Inactivation may occur during action potentials; both naturally occurring and reversible
Slowing activation and deactivation disrupt neuronal communication, leading to potential seizure activity.

Discussion on pulse protocol and observations of control vs. mutated channels prompts analysis of activation/deactivation timing, with implications for therapeutic approaches and understanding epilepsy Mechanisms.

Importance of understanding ion channel kinetics as a crucial aspect of neurophysiology, linking structure to function and physiological impact.