MT6314 INTRO TO CNS DRUGS Flashcards
CNS DRUGS are among the most important tools for?
studying all aspects of CNS physiology.
Nearly ALL drugs with CNS effects act on?
specific receptors that modulates transmission
Unraveling the actions of drugs with known clinical efficacy led to what?
the hypotheses regarding the mechanism of disease.
Electrically excitable cell (via electrochemical process)
Neuron
Macrophages from bone marrow
Microglia
Limits penetration of substances
BBB
Found on the neuron for insulation
Myelin sheath
Wraps around the axons
Oligodendrocytes
Cell body is also known as?
Soma
Where the synaptic responses are integrated with high concentration of voltage gated sodium channels
Axon initial segment
Highly branched complex “trees”
Dendrites
Most drugs act on the CNS by?
changing ion flow through transmembrane channels of nerve cells
Two types of channels defined on the basis of the mechanism controlling their gating (Opening & closing)
Voltage Gated Channels
Ligand Gated Channels
VOLTAGE OR LIGAND: Respond to changes in membrane potential
VOLTAGE
VOLTAGE GATED ION CHANNELS are concentrated where?
INITIAL SEGMENT of the axons in nerve cells
VOLTAGE OR LIGAND: Responsible for fast action potentials
VOLTAGE
In voltage gated ion channels what channels are responsible for action potential propagation?
Sodium channels
What other parts of the neuron have voltage-sensitive ion channels for what specific elements?
Cell bodies and dendrites
potassium and calcium
What are the 2 CLASSES OF NEUROTRANSMITTER RECEPTORS?
- LIGAND-GATED ION CHANNELS OR IONOTROPIC RECEPTOS
- METABOTROPIC RECEPTORS
Types of Metabotropic receptors?
Diffusible Second Messenger Mediated Regulation
Membrane-delimited Regulation
METABOTROPIC OR LIGAND: Chemically-gated
LIGAND
What do ligand ion channels respond to?
Respond to chemical neurotransmitters (NTAs) that bind to receptor subunits of the channel
T or F: Ligand gated ion channels are sensitive to the membrane potentials
F, weakly sensitive
How many GPCRs?
7
T or F: In Metabotropic Receptors, binding results in the direct gating of a channel
F, does NOT result
Metabotropic receptors: If there is binding, what does it result to?
Binding engages the G-protein that results into production of SECOND messengers that modulates the voltage gated channels
Membrane delimited pathways mainly target what channels?
Calcium and Potassium
METABOTROPIC (Ca or K channel): Slow inhibition in postsynaptic
K
METABOTROPIC (Ca or K channel): inhibited when metabotropic is activated in post synaptic
Ca
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 - A receptor coupled to a G protein that modulates
the formation of diffusible second messengers (cAMP, IP3, DAG)
ROLE OF THE ION CURRENT CARRIED BY
THE CHANNEL?
Synapse
EPSPs
IPSPs
EPSP or IPSP:
Generated by
* Opening of sodium or calcium channels
* Closing of potassium channels in some synapses
EPSP
EPSP or IPSP: Depolarizing
EPSP
EPSP or IPSP: high Na, low K
EPSP
EPSP or IPSP: Hyperpolarizing
IPSP
EPSP or IPSP: high Ca2+
EPSP
EPSP or IPSP: Generated by opening of potassium or chloride channels
IPSP
EPSP or IPSP: high K+ and Cl-
IPSP
EPSP or IPSP: low Ca2+ at presynaptic
IPSP
Some drugs exert their effect through?
direct interactions with molecular components of ion channels on axons
Examples of some drugs 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
Most drugs exert their effect mainly where?
at the synapses
Drugs may act presynaptically to alter?
- Synthesis
- Storage
- Release
- Reuptake
- Metabolism of transmitter chemicals
What interferes with the action of second messengers?
Pre- and postsynaptic receptors for specific transmitters
Inhibits storage of cathecolamines
Reserpine
Inhibits synthesis of serotonin
Parachlorophenylalanine
Depletes monoamine synapses of transmitters by interfering with intracellular storage
Reserpine
Inhibits degradation of Acetylcholine
Anticholinesterase
Inhibits release of catecholamines
Amphetamine
2 TYPES OF NEURONAL SYSTEM IN CNS?
HIERARCHAL
NON-SPECIFIC/DIFFUSION
HIERARCHAL or NON-SPECIFIC: Contain large myelinated, rapidly conducting fibers
Hierarchal
HIERARCHAL or NON-SPECIFIC: Broadly distributed, with single cells frequently sending processes to many different parts of the brain
NON-SPECIFIC
HIERARCHAL or NON-SPECIFIC: Tangential organization
NON-SPECIFIC
Major excitatory transmitters of hierarchal system?
- Aspartate
- Glutamate
Small inhibitory interneurons transmitters in hierarchal system?
- Gamma amino butyric acid (GABA)
- Glycine
Periodic enlargements that contain transmitter vesicles
Varicosities
Where are varicosities located?
axons
Types of transmitters in Non-specific neuronal system?
- Noradrenergic Amines (NE, dopamine and serotonin)
- Peptides that act on metabotropic receptors
What part of the brain are the transmitters usually seen in a non-specific neuronal system?
compact cell group called locus caeruleus in the caudal pontine central gray matter
Marked effects on CNS functions of non-specific neuronal system?
- Attention
- Appetite
- Emotional states
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
* Produce the same sort of postsynaptic
response that is seen with physiologic
activation of the synapse
CHEMICALS ACCEPTED AS NTAs IN THE CNS
Acetylcholine
Dopamine
Norepinephrine
Opioid Peptides
GABA and Glycine
Glutamic Acid
Serotonin