7.1: Introduction to Pharmacology of CNS Drugs Flashcards
True or False
Nearly ALL drugs with CNS effects act on a specific receptors that modulates transmission.
True
True or False
CNS DRUGS are among the most important tools for studying all aspects of CNS physiology.
True
True or False
Unraveling the actions of drugs with known clinical efficacy led to the hypotheses regarding the mechanism of disease.
True
True or False
In ion channels & neurotransmitter receptors, most drugs that act on the CNS do so by changing ion flow through transmembrane channels of nerve cells.
True
What are the two channel types defined on the basis of the mechanism controlling their gating?
- Voltage-gated channels
- Ligand-gated channels
What are the channel types found in Voltage-Gated Channels?
- Sodium channels
- Potassium channels
- Calcium channels
This blocks channel from outside
Tetradotoxin (TTX)
Slows inactivation, shifts activation
Batrachotoxin (BTX)
Blocks “small Ca-activated” K channel
Apamin
Blocks “big Ca-activated” K small
Charybdotoxin
Blocks N-type channel
Omega conotoxin (ω-CTX-GVIA)
Blocks P-type channel
Agatoxin (ω-AGAIVA)
Nicotinic ACh receptor:
Irreversible antagonist
α-Bungarotoxin
Blocks GABA-A receptor
Picrotoxin
Glycine receptor:
Competitive antagonist
Strychnine
Blocks AMPA receptor channel
Philanthotoxin
What are the channel types found in Ligand-Gated Channels?
- Nicotonic ACh receptor
- GABA-A receptor
- Glycine receptor
- AMPA receptor
Identify if Voltage or Ligand:
- Respond to changes in membrane potential
- Concentrated on the INITIAL SEGMENT of the axons in nerve cells
- Responsible for FAST action potentials
Voltage-gated ion channels
The voltage-gated ion channels includes the sodium channels responsible for?
Action potential propagation
True or False:
The voltage-gated ion channels have cell bodies and dendrites also have voltage-sensitive ion channels for potassium and calcium.
True
What are the two classes of neurotransmitter receptor?
- Ligand-gated ion channels or Ionotropic receptors
- Metabotropic receptors
Identify if Ionotropic or Metabotropic:
- Chemically-gated
- Respond to chemical neurotransmitters (NTAs) that bind to receptor subunits of the channel
Ionotropic Receptors
Identify if Ionotropic or Metabotropic:
- SEVEN transmembrane G protein coupled
- Binding does not result in the direct gating of a channel
- Binding engages the G-protein that results into production of SECOND messengers that modulates the voltage gated channels
Metabotropic Receptor
What are the two channels in metabotropic receptors that delimited the pathways of the membrane?
- Potassium channels
- Calcium channels
Types of receptor channel coupling in LIGAND GATED ion channels activation and inactivation:
- A receptor that acts directly on the channel protein
- A receptor that is coupled to the ion channel
through a G protein
Three receptors that are coupled to a G protein that modulates the formation of diffusible second messengers:
A. cyclic adenosine monophosphate (cAMP)
B. inositol trisphosphate (IP3)
C. diacylglycerol (DAG)
What are the two types of synapse?
- Excitatory Postsynaptic Potentials (EPSPs)
- Inhibitory Postsynaptic Potentials (IPSPs)
Identify if EPSPs or IPSPs:
- Depolarizing potential change
- Opening of sodium or calcium channels
- Closing of potassium channels in some synapses
Excitatory Postsynaptic Potentials (EPSPs)
Identify if EPSPs or IPSPs:
↑ Na+, ↓K+, ↑ Ca+2
Excitatory Postsynaptic Potentials (EPSPs)
Identify if EPSPs or IPSPs:
- Hyperpolarizing potential change
- Opening of potassium or chloride channels
Inhibitory Postsynaptic Potentials (IPSPs)
Identify if EPSPs or IPSPs:
↑ K+, ↑ Cl- at the postsynaptic, ↓Ca+2 at the presynaptic
Inhibitory Postsynaptic Potentials (IPSPs)
What are the drugs that exert their effect through direct interactions with molecular components of ion channels on axons?
- Carbamazepine
- Phenytoin
- Local anesthetics and some drugs used for general anesthesia
True or False:
In sites and mechanisms of drug action, most drugs exert their effect mainly at the synapses.
True
Inhibits synthesis of serotonin
Parachlorophenylalanine
Inhibits storage of cathecolamines
Reserpine
Inhibits release of catecholamines
Amphetamine
Inhibits degradation of Acetylcholine
Anticholinesterase
What are the two types of neuronal system?
- Hierarchical system
- Diffused/Non-specific Neuronal System
Identify if Hierarchical or Diffused Non-Specific:
- Contain large myelinated, rapidly conducting fibers
- Control major sensory and motor functions
- Excitability of the CNS
Hierarchical system
What are the two major excitatory transmitters in hierarchical system?
- Aspartate
- Glutamate
What are the small inhibitory interneurons transmitter in the hierarchical system?
- Gamma amino butyric acid (GABA)
- Glycine
Identify if Hierarchical or Diffused Non-Specific:
Broadly distributed, with single cells frequently sending processes to many different parts of the brain-tangential
Diffused Non-Specific
Periodic enlargements that contain transmitter vesicles and is located in the axons.
Varicosities
Peptides that act on metabotropic receptors and is found primarily in a compact cell group called locus caeruleus in the caudal pontine central gray matter.
Transmitters
Varicosities is located in the:
Axons
Transmitters are located in the:
Locus caeruleus in the caudal pontine central gray matter
What are the marked effect on CNS functions in the diffused/non-specific neuronal system?
- Attention
- Appetite
- Emotional states
What are the criteria for transmitter status?
- Present in higher concentration in the synaptic area than in other areas (localized in appropriate areas)
- Released by electrical or chemical stimulation via a calcium-dependent mechanism
- Synaptic mimicry
Identify this neurotransmitter in the CNS:
- 5% of neurons have receptors for Ach
- G protein-coupled muscarinic M1 receptors
- Slow excitation
- Decrease permeability to potassium
Acetylcholine (Ach)
Identify this neurotransmitter in the CNS:
- Inhibitory actions at synapses in specific neuronal systems
- G protein-coupled activation of K+ channels
- D2 receptor is the main dopamine subtype
- Increase cAMP
Dopamine
What are the excitatory effects of norepinephrine?
- Activation of α1 and β1 receptors
- Decrease K+ conductance
What are the inhibitory effects of norepinephrine?
- Activation of α2 and β2 receptors
- Increase K+ conductance
Identify this neurotransmitter in the CNS:
- Multiple 5 hydroxytryptamine (5-HT) receptor subtypes
- Metabotropic
- Inhibitory at many CNS sites
- Excitatory depending on the receptor subtype activated
Serotonin
Identify this neurotransmitter in the CNS:
- Excitatory for most neurons
- N-methyl-D-aspartate (NMDA) receptor
- Learning and memory
- Inhibition of adenyl cyclase
Glutamic acid
Identify this neurotransmitter in the CNS:
- Primary NTA mediating IPSPs
- GABA-A & GABA-B receptor activation
- Glycine is more numerous in the cord
- Glycine is inhibitory
GABA and Glycine
Function of GABA-A receptor activation in GABA and Glycine:
Opens Cl- conductance
Function of GABA-B receptor activation in GABA and Glycine:
- Opens K+ channels
- Closes Ca+2 channels
Identify this neurotransmitter in the CNS:
- Beta-endorphins, dynorphins
- Inhibitory (presynaptic)
- Decrease Ca+2 conductance
- Inhibitory (postsynaptic)
- Increase K+ conductance
Opioid peptides
Identify the specific receptor antagonist/s of Acetylcholine
(Mechanisms)
Excitatory:
⬇ in K+ conductance;
⬆ IP3, DAG
Pirenzepine, atropine
Identify the specific receptor antagonist/s of Acetylcholine:
(Mechanisms)
Inhibitory:
⬆in K+ conductance; ⬇ cAMP
Atropine, methoctramine
Identify the specific receptor antagonist/s of Acetylcholine:
(Mechanisms)
Excitatory: ⬆ cation conductance
Dihydro-B-erythroidine, a-bungarotoxin
Identify the specific receptor antagonist/s of Dopamine:
(Mechanisms)
Inhibitory (?): ⬆cAMP
Phenothiazines
Identify the specific receptor antagonist/s of Dopamine (D2):
(Mechanisms)
Inhibitory (presynaptic) ⬇Ca2+;
Inhibitory (postsynaptic): ⬆in K+ conductance, ⬇ cAMP
Phenothiazines, butyrophenones
Identify the specific receptor antagonist/s of GABA-A muscimol:
(Mechanisms)
Inhibitory: ⬆︎Cl- conductance
Bicuculline, picrotoxin
Identify the specific receptor antagonist/s of GABA-B baclofen:
(Mechanisms)
Inhibitory (presynaptic): ⬇︎Ca2+ conductance; Inhibitory (postsynaptic): ⬆︎K+ conductance
2-OH saclofen
Identify the specific receptor antagonist/s of Glutamate:
(Mechanisms)
Excitatory: ⬆︎ cation conductance, particularly Ca2+
2-Amino-5-phosphonovalerate, dizocilpine
Identify the specific receptor antagonist/s of Glutamate:
(Mechanisms)
Excitatory: ⬆︎cation conductance
NBQX, ACET
Identify the specific receptor antagonist/s of Glutamate:
(Mechanisms)
Inhibitory (presynaptic): ⬇︎Ca2+ conductance, ⬇︎cAMP; Excitatory: ⬇︎K+ conductance, ⬆︎IP3, DAG
MCPG
Identify the specific receptor antagonist/s of Glycine:
(Mechanisms)
Inhibitory: ⬆︎Cl- conductance
Strychnine
Identify the specific receptor antagonist/s of Serotonin (5-Hydroxytryptamine):
(Mechanisms)
Inhibitory: ⬆︎K+ conductance, ⬇︎cAMP
Metergoline, spiperone
Identify the specific receptor antagonist/s of Serotonin (5-Hydroxytryptamine):
(Mechanisms)
Excitatory: ⬇︎ K+ conductance, ⬆︎ IP3, DAG
Ketanserin
Identify the specific receptor antagonist/s of Serotonin (5-Hydroxytryptamine):
(Mechanisms)
Excitatory: ⬆︎cation conductance
Ondansetron
Identify the specific receptor antagonist/s of Serotonin (5-Hydroxytryptamine):
(Mechanisms)
Excitatory: ⬇︎ K+ conductance
Piboserod
Identify the specific receptor antagonist/s of Norepinephrine:
(Mechanisms)
Excitatory: ⬇︎K+conductance, ⬆︎IP3, DAG
Prazosin
Identify the specific receptor antagonist/s of Norepinephrine:
(Mechanisms)
Inhibitory (presynaptic): ⬇︎Ca2+ conductance; Inhibitory: ⬆︎K+ conductance, ⬇︎cAMP
Yohimbine
Identify the specific receptor antagonist/s of Norepinephrine:
(Mechanisms)
Excitatory: ⬇︎K+conductance, ⬆︎ cAMP
Atenolol, practolol
Identify the specific receptor antagonist/s of Norepinephrine:
(Mechanisms)
Inhibitory: may involve ⬆︎ in electrogenic sodium pump; ⬆︎cAMP
Butoxamine
Identify the specific receptor antagonist/s of Histamine:
(Mechanisms)
Excitatory: ⬇︎K+ conductance, ⬆︎IP3, DAG
Mepyramine
Identify the specific receptor antagonist/s of Histamine:
(Mechanisms)
Excitatory: ⬇︎K+ conductance, ⬆︎cAMP
Ranitidine
Identify the specific receptor antagonist/s of Histamine:
(Mechanisms)
Inhibitory autoreceptors
Thioperamide
Identify this neurotransmitter in the CNS:
Receptor Antagonist - Naloxone
Mechanism- Inhibitory (presynaptic): ⬇︎Ca2+ conductance, ⬇︎ cAMP
Inhibitory (postsynaptic): ⬆︎K+ conductance, ⬇︎ cAMP
Opioid peptides
Identify this neurotransmitter in the CNS:
Receptor Antagonist - Suvorexant
Mechanism - Excitatory, glutamate co-release
Suvorexant
Identify the specific receptor antagonist/s of Tachykinins:
(Mechanisms)
Excitatory: ⬇︎K+ conductance, ⬆︎IP3, DAG
Aprepitant, Sardutant, Osanetant
Identify the specific receptor antagonist/s of Endocannabinoids:
(Mechanisms)
Inhibitory (presynaptic): ⬇︎Ca+ conductance, ⬇︎ cAMP
Rimonabant