Chapter 4, The Chemistry of Behaviour Flashcards
What does Neurochemistry focus on?
The basic chemical composition and processes of the nervous system
What is Neuropharmacology?
The study of compounds that selectively affect the nervous system.
What is Neurochemistry?
The branch of neuroscience is concerned with the fundamental chemical composition and processes of the nervous system.
What is Exogenous?
Arising from outside the body.
Explain the versatility of Neurotransmitters.
May activate ionotropic receptors at some synapses.
- Different NT for different subtypes of receptor
- 14 subtypes for serotonin, 5 for Dopamine, 5 for Norepinephrine
May activate a metabotropic receptor at another synapse.
What is an Ionotropic Receptor?
Also called a Ligand-gated ion channel and chemically gated ion channel. A receptor protein includes an ion channel that is open when the receptor is bound by an agonist.
What is a Metabotropic Receptor?
A receptor protein that does not contain an ion channel but may, when activated, use a G-protein second-messenger system to alter the functioning of the postsynaptic cell.
What is a Receptor?
Also called receptor molecule. A protein that binds and reacts to molecules of a neurotransmitter or hormone.
What are the criteria for Neurotransmitters in the Presynaptic cell?
- Substance exists in presynaptic axon terminals
- Is synthesized in presynaptic cells
- Is released when action potentials reach axon terminals.
What are the criteria for Neurotransmitters in the Postsynaptic cell?
- Receptors for the substance exist on the postsynaptic membrane.
- When experimentally applied, the substance produces changes in postsynaptic cells
- Blocking substance release prevents changes in the postsynaptic cell
What are the types of Neurotransmitters (NT)?
- Amine NT = Acetylcholine, Dopamine, Serotonin, epinephrine, norepinephrine, melatonin
- Amino Acid NT = Gamma-aminobutyric acid (GABA), Glutamate, aspartate,
- Peptide NT (or neuropeptides) = Short-chain amino acids
- Gas NT = Soluble gases; nitric oxide, carbon dioxide.
What is Co-localization (co-release)?
Occurs when nerve cells contain more than one type of neurotransmitter.
A Neurotransmitter is what for a particular receptor?
An endogenous ligand
What is the name of a drug that can bind to a receptor and activate it?
A receptor agonist
Can drugs also act as agonists?
Yes, if they block reuptake or degradation of a Neurotransmitter.
What is the name of a drug that can bind to a receptor but does not activate it?
A receptor antagonist
What can Receptor Antagonists be?
It can be competitive (when they bind to the same site as the endogenous ligand)
Or they can be non-competitive or neuromodulators (when they bind to an alternate site and prevent the receptor from activating).
Can drugs interfere with synaptic transmission?
Yes, drugs can interfere with the many different processes involved in synaptic transmission.
What is Glutamate?
It is a major excitatory NT in the CNS.
- Most of the activity in the brain results from glutamate signaling.
- There are ionotropic and metabotropic glutamate receptors.
- To terminate glutamatergic synaptic transmission, glutamate is taken up by neighboring astrocytes.
What is GABA?
A major inhibitory NT in the CNS.
-Inhibition plays a very important role in brain function. GABA signaling is responsible for many of the IPSP’s generated in the brain.
What is Glutamatergic?
Referring to cells that use Glutamate as their synaptic transmitter.
What is Excitotoxicity?
The property by which neurons die when overstimulated, as with large amounts of Glutamate.
What are some of the Ionotropic Glutamate receptors?
- AMPA
- NMDA
- Kainate
The binding of glutamate to ionotropic receptors results in what?
The opening of a sodium ion channel.
Activation of the Metabotropic Glutamate receptors can be either what?
- Excitatory
- Inhibitory
What are the Gamma-aminobutyric (GABA) receptors divided into?
- GABA(A)—ionotropic, producing fast, inhibitory effects
- GABA(B)—metabotropic, slow inhibitory effects
- GABA(C)—ionotropic with a chloride channel
What GABA agonist is a potent tranquilizer?
Valium
What is Phencyclidine (PCP)?
It is an NMDA receptor antagonist. Originally developed as an anesthetic, PCP is considered a dissociative hallucinogen as it produces feelings of depersonalization and detachment from reality.
What is Ketamine (Special K)?
It is a less potent NMDA antagonist that has similar effects to PCP.
How do you terminate Gamma-amn=inobutyruc (GABA)?
To terminate GABA synaptic transmission, GABA is taken up by neighboring astrocytes.
What are the kinds of GABA receptors?
- Ionotropic
- Metabotropic
What are GABA(A) receptors?
They are receptors that are ionotropic, and activation of a GABAA receptor results in the opening of a chloride ion (Cl-) channel. This causes hyperpolarization of the postsynaptic cell (IPSP).
What interacts with GABA(A) receptors?
- Benzodiazepines (like Valium), barbiturates, and alcohol all interact with the GABAA receptor and potentiate (enhance) the effects of GABA. (GABA receptor agonists)
- These drugs are all anxiolytics, meaning they can reduce feelings of anxiety.
How was Acetylcholine (ACh) mapped?
By the enzymes involved in its synthesis
What is Acetylcholine (ACh)?
A neurotransmitter produced and released by parasympathetic postganglionic neurons, by motor neurons, and by neurons throughout the brain
Where is Acetylcholine (ACh) present?
- The PNS, including all neuron to muscle synapses (neuromuscular junctions) and in both divisions of the ANS.
- Present in many regions of the CNS including the basal forebrain and regions within the hindbrain.
What Cholinergic?
Referring to cells that use Acetylcholine as their synaptic transmitter.
Cholinergic nerve cell bodies and projections contain ACh.
- Lost in Alzheimer’s disease
- Involved with learning and memory
What degrades (ACh) and where?
Acetylcholinesterase (AChE) degrades ACh in the synaptic cleft.
What can (ACh) be divided into?
- Nicotinic receptors
- Muscarinic receptors
What are Nicotinic receptors?
Referring to cholinergic receptors that respond to nicotine as well as to acetylcholine.
- There are many different nicotinic receptors
- Nicotinic receptors are ionotropic.
- Initially named “nicotinic” because (many of) these receptors are sensitive to nicotine
What are Muscarinic receptors?
Referring to cholinergic receptors that respond to the chemical muscarine as well as to acetylcholine.
- There are many different muscarinic receptors
- Muscarinic receptors are metabotropic
- Initially named muscarinic because these receptors are sensitive to muscarine
What are the roles of Acetylcholine?
- ACh is important for all muscle contractions.
- ACh is important for the function of the sympathetic and parasympathetic divisions of the ANS
- ACh in the CNS is associated with attention, cognition, and memory.
Cholinergic cells degenerate in what disease?
Alzheimer’s disease.
What are the symptoms of Alzheimer’s disease?
The symptoms of Alzheimer’s disease (including memory loss and dementia) are thought to result from the loss of cholinergic neurons in the brain.
This suggests that ACh signaling normally supports memory formation and cognition.
What are Acetylcholine Agonists?
- Nicotine
- Sarin
What is Nicotine?
It is a nicotinic acetylcholine receptor (nAChR) agonist – nicotine is a stimulant, it can enhance cognitive functions (like attention and memory), and increase feelings of pleasure.
Nicotine is also rewarding and reinforcing, making it addictive.
What is Sarin?
It is a synthetic AChE inhibitor – used as a chemical weapon.
Causes convulsions, over-activation of the ANS, suffocation, and death.
What are Acetylcholine Antagonists?
- Curare
- Scopolamine
What is Curare?
nAChR antagonist - causes paralysis, used in hunting
What is Scopolamine?
mAChR antagonist – can impair cognitive functions (like attention and memory formation)