Neuropharmacology Exam 1 - Chapter 1 (refined)

Define neuropharmacology.

The scientific study of the effects of drugs on the nervous system

Define psychotropic agents

Drugs that influence behavior

Define neuropsychopharmacology

All types of drug effects that influence N.S. functioning

Neuroscience complexity shown in comparing Fluoxetine and Furosemide

Fluoxetine - more complex; affects neurons that use serotonin as neurotransmitter (a few 100,000 / 100 billion neurons). Prevents serotonin reuptake, causes neural adaptation

Furosemide - direct and straightforward; inhibits Cl- channels in loop of Henle, more Cl- in lumen of nephron, more H20 → diuresis

Fluoxetine reflects drug-induced neural plasticity. What is meant by this?

Neurons and other cells adapt overtime to chronic disturbance

Monoamines, amino acids, purines, and peptides can all act as ____ in the NS.

Neurotransmitters

For each NT there are multiple receptors. This lead to the development of what? This lead to the recognition of what?

Led the the development of drugs with increased selectivity towards individual receptors. Recognition of postreceptor signal transduction cascades.

Studies on the effects of drugs on the nervous system provides crucial info into? Provide two examples.

Crucial information into intracellular signaling functions.

Ex: Organic nitrates cause vasodilation when treating cardiac angina → nitric oxide as critical signal molecules

Ex: NSAIDs → signaling molecules derived from arachidonic acid

Responsive adaptations to repeated drug exposure models what?

Those for other external exposures like stress

The ability of a drug to produce effect is dependent upon what three factors?

Absorption/penetration into tissues, stability, and elimination

Route of administration can determine (2)?

1) How rapidly a drug reaches its target organ

2) Which organs it affects

Name the 7 routes of administration. Which of these are considered parenteral?

1) oral → relatively slow onset of action

2) subcutaneous → under the skin

3) intraperitoneal → into the peritoneal-abdominal cavity

4) intravenous

5) intracerebroventricular → into the cerebral ventricular system

6) intrathecal → into spinal fluid

7) intracerebral → into functional brain tissue

#2-7 considered parenteral

Define bioavailability (of a drug).

Amount that enters general circulation which determines how much drug is available to reach its target

The bioavailability of a drug is influenced by (4):

Absorption (from the gut, if oral), binding of drug to plasma proteins (drug unavailable to bind to target), ability to penetrate BBB, permeate membranes if acting on intracellular proteins

Drug action depends on stability once absorbed. What is meant by this?

How rapidly it is metabolized to inactive congeners or eliminated through urine/bile/air. Note that prodrugs must be converted to active metabolites to exert biological effect.

Bioavailability and stability are _____ considerations. Define this term, as well as pharmacodynamic and pharmacogenetics.

Pharmacokinetic - movement of drugs within the body

Pharmacodynamic - mechanisms of drug action

Pharmacogenetics - influence of individual’s genes in determining drug response

Initial target of drug generally determines the: (2)

Cells and neural circuits on which the drug acts, potential efficacy + side effects

Drug binds protein → affects protein functioning. A drug can conceivably bind any protein site: simple and complex sites. Define these terms.

Simple sites: a few continuous A.A residues on protein’s primary structure

Complex sites: discontinuous residues on primary structure brought near 2/3 structure

_____ and ____ of receptor (drug binding site) must complement that of drug. Interaction of drug + binding site can influence _____ or _____

Conformation (3D) and electrostatic charge; intrinsic activity of protein (ex. catalytic activity) OR ability of protein to interact w/other molecule (ex. receptor binding NT)

Binding “rules”

• Ligand binding should be specific → must bind specific target protein

• Many cases binding is stereoselective → specific to one stereoisomer of drug

• Binding should be saturable →Tissue has finite # of receptor proteins

• Binding should attain a steady state → state of equilibrium allowed by incubation conditions

In the ideal situation, binding to receptor site is ____ + _____

Competitive + fully reversible

How to determine specific + nonspecific binding in experiment with radioactive ligand/drug

Flood tissue w/ untagged drug which kicks out tagged from receptor, watch radioactive signal disappear → specific binding

Flooding area with untagged drug won’t displace tagged drug from cell glass, signal that stays → nonspecific binding

Discrepancies between ideal and actual situations in terms of radioactive drug experiment arise because (3):

1) irreversible binding → some drugs bind permanently

2) artifactual sites → random, non-target cell structures mimic real receptors & signal

3) multiple subtypes → drug might being to several different receptor subtypes

Specific drug binding boils down to…

how many receptor sites exist & drug affinity

• Bmax (maximum binding capacity): total number of available target receptors sets a ceiling on specific binding

• Kd (dissociation constant/affinity): drug conc required to fill 50% of total receptor sites (i.e. measures stickiness)

Compare a Kd of 1 nm versus that of 100 nm. Explain

1 nm = high affinity; drug binds so well that low concentration fills 50%

100 nm = low affinity; high conc of drug needs to be present

Sigmodial curve and Scatchard plot for specific drug binding

Sigmodial curve: ligand binding plotted as function of the log of drug conc

Scatchard plot transforms curve into straight line. Plots bound/free on y-axis, total bound on x. X-intercept = Bmax, Slope = -1/Kd

Describe competition curves

Another method for studying ligand-target interactions. Flood w/unlabeled drug. Ki (inhibition constant) is the exact concentration of new drug required to displace 50% of radioligand (measure of new drug affinity). Historically aided with discovery of multiple subtypes. Receptor autoradiography if performed on brain sections.

Factors that can affect ligand binding / ways to combat these

The radioligand, salt and ionic content of buffer, presence of different guanine nucleotides. Cloning of receptors and ability to express them on cells without endogenous expression

Practice radioligand experiments from slideshow.

Describe the two distinct aspects of drug action.

Potency (affinity, Kd) describes the binding strength between a drug and its target. Efficacy is the biological effect exerted on the target following drug binding.

Define an orthosteric site.

the site at which an endogenous NT binds to a receptor to produce the conformational changes required to activate the receptor.

Define an agonist

Binds to the orthosteric site on a receptor to mimic action of endogenous NT

Define an antagonist.

Inert, exert a biological effect only by interfering with endogenous ligand. Can bind an orthosteric site or other site on receptor

If an antagonist does bind at the orthosteric site, it…

will not cause conformational changes required to engage downstream signaling processes

Contrast a competitive versus noncompetitive antagonist.

Can reduce the actions of an endogenous ligand by competing for the same site; can bind elsewhere and prevent receptors from shifting to active conformation, ligand still able to bind orthosteric site

Characterize morphine, ketamine, and naloxone as type of drug each is.

Morphine: agonist for endogenous opioid peptides

Naloxone: competitive antagonist

Ketamine: noncompetitive antagonist because binds to a site on the receptor different from the site that binds glutamate and prevents glutamate from opening the ion channel intrinsic to the receptor

Differences in efficacy between agonists and competitive antagonists are independent of the affinity with which they bind the orthosteric site. Why?

Antagonist may lack another moiety required for efficacy even if it has one required for receptor binding.

Define partial agonist (mixed agonists-antagonists)

Drug binds to orthosteric site of a receptor and elicits only a partial biologic response

Effects of high-potency partial agonists on net receptor activity under low vs. high endogenous tone

Under low tone, acts as an agonist by raising activity to its submaximal celling. Under high tone, acts as an antagonist by displacing full agonists *natural NT and lowering total signaling to the same ceiling

Ex. Buprenorphine is a partial agonist at opioid receptors

Can treat chronic pain/addiction. At low doses, elicits a mild analgesic and rewarding effect. Higher doses fail to yield stronger effect and instead antagonize the action of full opioid agonist (ex. morphine)

Define an inverse agonist and requirement of the receptor it binds.

Bind to orthosteric site and elicits biological response opposite of an agonist. Receptor must have basal activity to run down

If an inverse agonist closes an ion channel, an agonist…

Opens an ion channel

Define an allosteric site

Binding to can influence function of receptors.

Define positive allosteric modulators (PAMs)

Ligands that bind the allosteric site to facilitate agonist-induced activation of the receptor. PAM cannot influence receptor function without orthosteric agonist.

Define NAMs

Ligands that bind the allosteric site to reduce the effect of agonist induced activation of the receptor

All NAMs can be viewed as noncompetitive antagonists of a receptor, but not all noncompetitive antagonists are NAMs. Why?

Some noncompetitive antagonists can antagonize a receptor in the absence of an orthosteric agonist.

Drugs should be thought of as existing on a continuum ranging form ____ to ____ to ____.

Full agonist to inert antagonist to full inverse agonist

How does the GABAa receptor function at its orthosteric site, and how do Muscimol and Bicuculline interact with it?

Mechanism: Opens a Cl- ion channel, letting chlordie stream in to hyperpolarize and calm neural firing

Endogenous Agonist (GABA): Primary calming NT

Exogenous Agonist (Muscimol): Binds the main door to open the channel directly, mimicking GABA.

Antagonist (bicuculline): Plugs the main door, blocking GABA from entering and opening the channel

How do PAMs, SAMs, and NAMs alter GABAa receptor activity at allosteric sites, and what drugs represent each class?

• PAM (Diazepam): Modulates the receptor shape so GABA sticks better and activates the channel more strongly (increases calming).

• SAM (Flumazenil): Physically blocks the allosteric site to prevent PAM binding, but has no effect of its own on GABA action.

• NAM (beta-carbolines): Twists receptor conformation so GABA works worse, decreasing inhibition and spiking anxiety.

Classify GABA, Muscimol, Bicuculline, Diazepam, Flumazenil, and beta-carboline by their binding site and pharmacological action at the GABAa receptor.

• Orthosteric Site:

  • GABA: Endogenous Agonist (increase Cl- influx)

  • Muscimol: Exogenous Agonist (increase Cl- influx)

  • Bicuculline: Competitive Antagonist (Blocks GABA)

• Allosteric Site:

  • Diazepam: Positive Allosteric Modulator (PAM - enhances GABA)

  • Flumazenil: Silent Allosteric Modulator (SAM - blocks PAMs)

  • beta-carboline: Negative Allosteric Modulator (NAM - reduces GABA)

Two distinct receptor types can physically lock together and form a heterodimer. What is the effect?

Super-receptor adopts a unique shape and has brand new binding properties. Drugs with low affinity for either receptor alone can latch onto complex with high affinity now.

Intrinsic efficacy is no longer about ____ (quantitative) but what _____ (qualitative).

How much signal a drug generates; what specific internal pathway turns on

Different drugs binding to the exact same receptor can twist it into slightly different shapes, directing the receptor to…

signal one specific pathway

Define ligand directed or biased signaling

Different agonists at a given receptor can direct the receptor to signal via distinct intracellular pathways

Binding sites with a high affinity for drugs do not necessarily have…

an endogenous ligand

The effect of a drug on a target protein is dependent on

concentration of the drug

A rightward, or downward shift in a dose-dependent drug response curve indicates…

a reduction in drug sensitivity; more drug is needed at all concentrations to elicit the same level of biologic response

An inverted U-shaped curve means that more drugs are better to an extent. Taking too much drug actually causes the biological response to drop back down. AT high doses…

Concentration is so high drug spills over into other secondary receptors. Flooding the main target with too much drug overstimulates them; receptors fatigue & lock up so they no longer respond.

Why must you test a full dose-response curve (instead of a single dose) for drugs with inverted U-shaped responses?

The Single Dose Trap: Because the curve goes up and then down, testing just one drug dose can lead to wrong conclusions if the curve shifts left or right.

Depending on the dose you pick to measure:

• At low doses: The shifted drug looks more effective (climbing earlier)

• At mid doses: The shifted drug looks unchanged (where curves cross)

• At high doses: The shifted drug looks less effective (falling down the far side)

How do PAMs and NAMs alter a drug’s dose-response curve?

PAM (Turns Volume Up): shifts curve left (increases potency/takes less drug to work), shifts curve up (increases maximum response)

NAM (Turns Volume Down): shifts curve right (decreases potency/takes more drug to work), shifts curve down (decreases maximum response)

Why do you need a full dose-response curve (rather than a single dose) to identify a PAM or NAM?

• Distinguishes Mechanics: Modulators can change potency (left/right shift), peak efficacy (up/down shift), or both. A single point won't tell you which occurred.

• Reveals True Net Effect: On complex or inverted U-shaped curves, measuring a single dose after adding a PAM/NAM can misrepresent whether receptor function was enhanced or suppressed overall.

Drug binding influences the function of a protein by…

either facilitating or inhibiting that protein’s normal function, including its interactions with other molecules. Some drugs can create a new function for the protein they bind (FK506).

Major setbacks of the Black Box approach in which researches gave drug to an animal → observed the effect:

• It misses the full chain reaction (molecule → behavior). Knowing a drug’s primary target doesn’t explain how it cures a patient

• Misidentified/misclassified proteins. Used to guess what receptors looked like based on potency tests.

Structure-activity relationships to determine…

what types of chemical moieties can be added to a drug to alter its actions on a protein target

What is the difference between "clean" and "dirty" drugs, and why are "dirty" drugs often more clinically effective?

• Clean (Selective): Binds to only one specific receptor protein. Designed to avoid side effects, but often disappointing for complex brain conditions.

• Dirty (Polypharmacological): Binds to multiple different receptor types simultaneously.

• Clinical Takeaway: Complex psychiatric disorders involve multiple brain circuits, so multi-target ("dirty") drugs often produce better clinical results than single-target drugs.

What is the difference between molecular specificity and systems specificity?

• Molecular Specificity: How selectively a drug binds to a single target protein (e.g., fluoxetine targeting only the serotonin transporter).

• Systems Specificity: How localized the drug's ultimate biological effect is across the brain network.

• Key Takeaway: High molecular specificity does NOT guarantee high systems specificity. Inhibiting one single transporter can flood the brain with neurotransmitters and indirectly trigger dozens of downstream receptor subtypes.

Define functional genomics and proteomics

The processes of sequencing, identifying, and characterizing individual gene products

What are gene networks in modern neuropharmacology, and how do they reveal new drug targets?

• Definition: Bioinformatic maps tracking global changes in gene expression across specific brain cells after drug exposure.

• Purpose: Traces the ripple effects of a drug to identify core "driver" regulatory proteins, which can then be targeted directly with new medications.

 What is phenotypic screening, and how does proteomics complement it in drug discovery?

• Phenotypic Screening: Testing compounds to see if they produce a desired biological effect/behavior first, without knowing which protein target they actually hit.

• Role of Proteomics: Once a compound is proven to work in the screen, proteomics is used to work backward and identify the exact mystery protein target the drug bound to.

What are 3 main strategies for targeting RNA directly in drug therapy?

• 1. Small Molecules: Tweak splicing or cellular translation machinery to adjust RNA expression levels.

• 2. Antisense Oligonucleotides (ASOs): Short synthetic nucleic acid strands (~20 nucleotides) that bind complementary target mRNA to block translation, modify splicing, or trigger degradation.

• 3. MicroRNAs (miRNAs): Short strands (~20 nucleotides) that bind specific target RNAs to inhibit translation or alter splicing.

What is Nusinersen, how is it delivered, and how does it treat Spinal Muscular Atrophy (SMA)?

• Drug Class: Antisense Oligonucleotide (ASO).

• Delivery: Intrathecal injection (directly into spinal fluid to reach the CNS).

• Mechanism: Binds complementary RNA to alter SMN2 gene splicing, restoring functional SMN protein expression in motor neurons.

How do Antisense Oligonucleotides (ASOs) target neurodegenerative diseases like Huntington's and ALS?

• Target: Mutated RNA transcripts encoding toxic proteins.

• Mechanism: ASOs bind complementary mutant RNA sequences to prevent translation or alter splicing, preventing toxic protein buildup in neurons.

Viral-mediated gene therapy shows promise for retinitis pigmentosa, which involves degeneration of the retina. Most of these approaches use different subtypes of adeno-associated viruses, which…

mediate long-lived transgene expression without serious side effects

Direct injection of AAVs into the brain are ongoing for ___ & ____. Systemic delivery of AAVs is under investigation for _____.

Parkinson disease and epilepsy; spinal muscular atrophy (SMA)

Enzyme termed Cas9 is a _____ that ______. It is tethered to _____.

nuclease; cleaves/disrupts the targeted genomic region; a single guide RNA that targets the complex to a single region of the genome of complementary sequence to the sgRNA.

Enzymatically dead Cas9 can be fused to any functional moiety, a DNA or histone methylating enzyme, to

induce more subtle effects of the epigenetic state of the targeted gene and its expression levels within the targeted cells.

Describe Chimeric Antigen Receptor T cell therapies.

T cells are first isolated from a patient and engineered by CRISPR to increase ability of the cells to recognize/neutralize cells more effectively, then infused back into patient.

What is pharmacogenetics, and how does it advance treatment for complex CNS disorders?

• Concept: Using an individual's genetic and "omic" profile (transcriptomics, metabolomics) to predict drug response.

• CNS Application: Divides broad, heterogeneous conditions (e.g., autism, schizophrenia, epilepsy) into distinct biological subtypes, allowing drugs to target specific underlying abnormalities rather than broad symptoms.

How do Cytochrome P450 (CYP) gene variants impact clinical drug dosing?

• Function: CYP enzymes metabolize the vast majority of drugs in the liver and brain.

• Clinical Impact: Genetic variations cause individuals to metabolize drugs much faster (ultrafast) or slower (poor) than normal, dictating whether a patient needs unusually high or low doses to prevent treatment failure or toxicity.

How do Tamoxifen and EGFR antagonists (gefitinib/erlotinib) demonstrate targeted therapy?

• Tamoxifen: Given only to patients whose breast tumors express estrogen receptors.

• EGFR Antagonists: Targeted to tumors with mutant EGFR signaling. Used in glioblastomas, where testing EGFR function predicts which ~20% of brain cancer patients will actually respond

What are induced pluripotent stem cells (iPSCs), and which 4 transcription factors create them?

• iPSCs: Skin cells (fibroblasts) reprogrammed back into embryonic-like stem cells capable of becoming any cell type in the body.

• The 4 Yamanaka Factors: OCT3/4, SOX2, c-MYC, and KLF4.

What is the main maturity limitation of neurons created from patient iPSCs?

• Embryonic State: iPSC-derived cells resemble early embryonic cells rather than fully mature adult neurons.

• Example: Induced "dopamine neurons" express tyrosine hydroxylase (the rate-limiting enzyme), but differ significantly from adult dopamine neurons in overall gene expression and function.

What are brain organoids, and what are their 3 main applications in neuropharmacology?

• Definition: 3D tissue structures grown from iPSCs that form layers of neurons and glia resembling the developing brain.

• 3 Applications:

  1. Disease Modeling: Studying complex genetic disorders like Alzheimer's and schizophrenia.

  2. High-Throughput Screening: Testing large drug libraries to see which compounds correct cell defects.

  3. Cell Therapy: Future potential for transplanting patient-derived cells back into the brain

What are the definitions and distinctions between Pharmacokinetics, Pharmacodynamics, and Pharmacogenomics?

Pharmacokinetics (ADME): How the body processes the drug (Absorption, Distribution, Metabolism, Excretion)

Pharmacodynamics: The molecular mechanism of action of the drug on its protein targets (what the drug does to the body)

Pharmacogenomics: How an individual’s genetic profile influences their response to specific drugs

Why does Fluoxetine take weeks to produce an antidepressant effect even though SERT inhibition occurs almost immediately?

• Anatomy: Only 100,000 serotonergic neurons exist in the brain, projecting to 95 billion neurons and 95 trillion synapses.

• Mechanism: The clinical antidepressant response is not driven by immediate SERT blockade, but by downstream neuroplasticity and long-term structural brain remodeling triggered by prolonged serotonin elevation.

How is specific receptor binding experimentally isolated from non-specific binding in tissue homogenates?

• Total Binding: Radiolabeled ligand bound to tissue.

• Displacement Trick: Add 1,000 times 1,000,000 molar excess of unlabeled ligand. Unlabeled drug displaces radioligand from finite, saturable receptor sites (Specific Binding).

• Nonspecific Binding: The remaining non-displaceable binding to infinite background sites (glass tube, lipids).

• Formula: Specific Binding = Total Binding - Nonspecific Binding

What do Bmax and Kd represent in receptor kinetics, and how does Kd relate to binding affinity?

• Bmax: Maximum specific binding capacity (total number of accessible receptors in the tissue).

• Kd: Equilibrium dissociation constant; the ligand concentration required to occupy 50% of Bmax

• Affinity Relationship: Kd is inversely proportional to affinity (Lower Kd = higher affinity/stronger binding).

What parameters are plotted on a Scatchard plot, and how are Bmax and Kd derived from its geometry?

Y-axis: Bound/free ligand ration

X-axis: Bound ligand (B)

X-intercept: Represents Bmax

Slope: Equals -1/Kd

Note: A curved Scatchard plot indicates multiple receptor subtypes or binding site affinities.

What is plotted on a competition binding curve, and what does the inhibition constant Ki measure?

• Y-axis: % Specific Binding of radioligand.

• X-axis: Log concentration of competing unlabeled drug.

• Ki (Inhibition Constant): Concentration of competing drug that displaces 50% of bound radioligand. Lower Ki = higher competitive potency against endogenous ligands.

How do potency and efficacy differ, and why is Buprenorphine (a partial agonist) preferred over Morphine (a full agonist) in opioid therapy?

• Potency (Kd): Drug concentration needed to produce a response.

• Efficacy (Emax): Maximum biological effect achievable.

• Clinical Utility: Buprenorphine has very high affinity (low Kd) to displace opioids, but lower intrinsic efficacy (Emax). It provides analgesia and suppresses withdrawal without causing maximal respiratory depression or high addiction risk.

Define Full Agonist, Partial Agonist, Neutral Antagonist, and Inverse Agonist in terms of biological intrinsic activity (Emax).

• Full Agonist (Emax = 100%): Maximally activates receptor.

• Partial Agonist (0 < Emax < 100): Submaximal receptor activation.

• Neutral Antagonist (Emax = 0%): Zero intrinsic activity; blocks agonists from binding.

• Inverse Agonist (Emax< 0%): Binds same site as agonist but suppresses baseline/constitutive activity, producing the opposite biological effect (e.g., Tamoxifen at estrogen receptors).

What is the difference between orthosteric and allosteric receptor sites, and how do PAMs work?

• Orthosteric Site: Primary binding site for endogenous neurotransmitters.

• Allosteric Site: Topographically distinct site on the receptor.

• PAM (Positive Allosteric Modulator): Binds allosteric site to alter receptor conformation, enhancing orthosteric ligand affinity or efficacy (e.g., Diazepam at GABAa receptors).

What does a leftward shift in a dose-response curve signify, and why do CNS drugs often show an inverted U-shaped curve?

• Leftward Shift: Indicates increased potency/sensitivity (e.g., CBT combined with antidepressants allows lower drug doses for equal effect).

• Inverted U-Shape: Increasing doses yields optimal therapeutic effect at peak, but higher doses engage off-target receptors or cause toxicity/desensitization.

• Modern Evolution: Discovery evolved from "Black Box" tissue responses to X-ray crystallography, enabling rational drug design aimed at structural binding pockets.

How do cocaine and caffeine illustrate the identification of neurotransmitter systems?

• Cocaine: Increases dopamine in the reward circuitry (dopaminergic system).

• Caffeine: Acts on purinergic (adenosine) receptors. Adenosine receptors also bind ATP, which functions as both an energy substrate and a neurotransmitter in pain signaling.

What did nicotine self-medication reveal about schizophrenia, and how was Furosemide used as a contrast?

• Nicotine: Widespread self-medication in schizophrenia helped uncover cholinergic system involvement in the disease's pathogenesis.

• Furosemide: A peripheral renal drug used to contrast simple organ pharmacology with the vast complexity of CNS networks (e.g., $100,000$ serotonin neurons targeting $95\text{ trillion}$ synapses).

What is the "Black Box" approach (using the NGF example)

Black Box Example: Nerve Growth Factor (NGF) was known to increase norepinephrine production in neurons before the intermediate intracellular signaling cascade was understood.