Pharmacodynamics (Exam 1) Flashcards
Agonist
Activator
Antagonist
Inhibitor
Endogenous
Naturally made
Xenobiotics
Synthetically made
Drug Targets
- Receptors
- Enzymes
- Ion Channels
- Transports/Carriers/Pumps
Types of Receptors
Ligand-Gated Ion Channels (LGIC)
G-Protein Coupled Receptors (GPCR)
Enzyme-Linked Receptors
Intracellular Receptors
Affinity
Strength of attraction between drug and its binding site
Covalent
Strong and in many cases not reversible
Least Common
Electrostatic
Vary from relatively strong linkages to weaker hydrogen bonds to van der Waals
Most Common
Hydrophobic
Important for highly lipid soluble drugs
Drug Response
Result of chemical interactions between a drug and binding site
Receptors
Transmembrane proteins located within cell membrane
How do receptors work?
Bind to ligand and propagate a signal leading to effect/response
Ligand
Molecule which produces a signal by binding to a site on receptor
Receptor Mediated Messenger System
First Messenger - ligand
Signal Transducer - receptors
Effector - enzymes activated by signal transduction
Second Messenger - Signaling molecules that activate other targets, allows for signal amplification
Autocrine Signaling
Ligand originates from same cell
Autoreceptor
Receptors whose purpose is to bind their own ligand as negative feedback mechanism
Paracrine Signaling
Ligand originates from nearby cell
Endocrine Signaling
Ligand originates from distant cell and travels through bloodstream
Hormones
Ligands of endocrine system
Ligand Gated Ion Channels (LGIC)
Ligand binding causes conformational change that opens channel allowing ions (Na+, Ca2+, K+, Cl-) to pass through
LGIC for Na+ and Ca2+
Excitatory
Make cell more positive, closer to threshold potential
LGIC for Cl- and K+
Inhibitory
Make cell more negative, farther from threshold potential
Acetylcholine (LGIC)
Nicotinic Receptor
LGIC (Na+)
Serotonin (LGIC)
5HT3 Receptor
LGIC (Na+)
Glutamate (LGIC)
NMDAR Receptor –> LGIC (Ca2+)
AMPAR Receptor –> LGIC (Na+)
GABA (LGIC)
GABA-A Receptor
LGIC (Cl-)
G-Protein Coupled Receptors (GPCRs)
Receptor bound to G-protein and leads to G-protein activation
Gs GPCRs
Activates adenylyl cyclase (AC)
Gi GPCRs
Inhibits adenylyl cyclase (AC)
Gq GPCRs
Activates phospholipase C (PLC)
What determines if receptor is Gs, Gi, or Gq?
The alpha subunit of G-protein
Gs Signaling Pathway
AC is activated and converts ATP to cAMP
cAMP acts as second messenger –> activates cAMP dependent protein kinases
Kinases phosphorylate other proteins
Gi Signaling Pathway
AC is inhibited
Sometimes K+ channels opened
Gq Signaling Pathway
Phospholipase C (PLC) is activated and converts PIP2 into DAG and IP3
DAG and IP3 act as second messengers
DAG activates PKC which activates other enzymes
IP3 causes Ca2+ release from intracellular storage
Ca2+ activates calmodulin –> other enzymes
Acetylcholine (GPCR)
M1, M3, M5 Receptor –> GPCR Gq
M2, M4 Receptor –> GPCR Gi
Norepinephrine/Epinephrine (GPCR)
alpha-1 receptor –> GPCR Gq
alpha-2 receptor –> GPCR Gi
beta1-3 receptor —> GPCR Gs
Dopamine (GPCR)
D1, D5 Receptor –> GPCR Gs
D2, D3, D4 Receptor –> GPCR Gi
Serotonin (GPCR)
5HT1, 5 Receptor –> GPCR Gi
5HT2 Receptor –> GPCR Gq
5HT4, 6, 7 Receptor –> GPCR Gs
Endogenous cannabinoids (GPCR)
CB1, CB2 Receptor –> GPCR G1
Endogenous opioids (GPCR)
Mu, delta, kappa Receptors –> GPCR Gi
Which receptor works quicker? GPCR or LGIC
LGIC because there’s no second messenger system
Activation of which receptor leads to increase in cAMP?
Gs coupled receptors
Enzyme-Linked Receptors
Linked to an enzyme that mediates downstream signaling
Alter gene expression to produce effects –> slow onset and long duration
Receptor Tyrosine Kinases
Enzyme within receptor
Ligand binds to receptor –> Conformational change leads to dimerization –> Activates tyrosine kinase function –> phosphorylation of tyrosine residue -> receptor becomes activated and phosphorylates downstream proteins
Which ligand uses receptor tyrosine kinases?
Insulin
Cytokine receptors
Enzyme as separate protein
Enzyme binds non-covalently and becomes activated following ligand binding and dimerization
Which ligand uses cytokine receptors?
Growth hormone
Intracellular/Nuclear Receptors
Ligand must be lipid soluble to cross cell membrane
Nuclear receptors bind to DNA and regulate gene expression
Contain ligand binding domain (LBD) and DNA binding domain (DBD)