Neuro 1 Exam 2
adrenaline (epinephrine)
fight or flight response focus & attention release of glucose for energy primarily produced & released by the adrenal glands involved in the stress response, increased heart rate/blood pressure/blood sugar/mental alertness, dilation of pupils/airways drug targets: alpha & beta adrenergic receptors
dopamine
influences movement, learning, attention, and emotion reward & pleasure, drive, and motor activity drug targets: D1 receptors (cAMP production) & D2 (modulate mood, reward, & motor function)
dopamine & caffeine
interaction b/w adenosine & dopamine signaling DA direct pathway "Go" - promotes voluntary movement DA indirect pathway "Stop" - inhibits thalamic activity and prevents voluntary movement
GABA transporter, antiporter, & receptor
transporter: GAT antiporter: vesicular GABA transporter (VGAT) receptors: GABA-A (ionotropic) & GABA-B (metabotropic)
Noradrenaline transporter, antiporter, & receptor
transporter: NET antiporter: vesicular monoamine transporter (VMAT2) receptor: alpha & beta adrenergic receptors
serotonin transporter, antiporter, & receptor
transporter: SERT antiporter: vesicular monoamine transporter (VMAT2) receptors: 5-HT receptors
acetylcholine transporter, antiporter, & receptor
transporter: choline transporter antiporter: vesicular acetylcholine transporter receptor: nicotinic & muscarinic
glutamate transporter, antiporter, & receptor
transporter: excitatory amino acid transporters (EEATs) antiporter: vesicular glutamate transporter (VGLUT) receptors: ionotropic or metabotropic glutamate receptors
AAV (adeno-associated virus)
-no immune response -limited expression affects neurons causing neurological diseases Using bioengineering approach to change genome Insert genes that you want to express inside the AAV
simple model of opioid analgesia
1. Substance P along with glutamate and other pain producing neurotransmitters produces depolarization potential in pain neuron 2. Opioid peptides and opioid drugs open ligand gated K+ channels to decrease the intensity of depolarization 3. Opioid receptors on sensory neurons when stimulated open Cl- ion channel and block Ca2+ channel to inhibit firing of sensory neuron
atypical neurotransmitter mechanism - endocannabinoid system
1. Synthesis and Release: Unlike typical neurotransmitters, cannabinoids like THC are not synthesized and released from presynaptic neurons in response to an action potential. Instead, they are produced on-demand in postsynaptic neurons and other cells in response to various stimuli or external substances, such as cannabis. 2. Endocannabinoid Synthesis: The most well-known endocannabinoids are anandamide (AEA) and 2-arachidonoylglycerol (2-AG). These endocannabinoids are produced from lipid molecules, particularly arachidonic acid, which is part of cell membranes. 3. Retrograde Signaling: Unlike traditional neurotransmitters that transmit signals from presynaptic neurons to postsynaptic neurons, endocannabinoids work in a retrograde manner. Postsynaptic neurons release endocannabinoids that travel backward across the synapse and bind to cannabinoid receptors on presynaptic neurons. 4. Cannabinoid Receptors: There are two primary types of cannabinoid receptors: CB1 receptors and CB2 receptors. CB1 receptors are primarily found in the central nervous system (CNS), especially in regions involved in pain perception, memory, and mood. CB2 receptors are primarily found in the immune system and peripheral tissues. 5. Activation of Cannabinoid Receptors: When endocannabinoids like anandamide or exogenous compounds like THC bind to CB1 receptors on presynaptic neurons, it results in the modulation of neurotransmitter release. Activation of CB1 receptors typically leads to a reduction in the release of other neurotransmitters, such as glutamate or gamma-aminobutyric acid (GABA), depending on the brain region. 6. Modulation of Synaptic Transmission: The activation of CB1 receptors by cannabinoids like THC can dampen neurotransmission at the synapse where it occurs. This modulation can lead to altered neuronal excitability. 7. Termination and Recycling: Endocannabinoid signaling is terminated through various mechanisms. One important mechanism involves the uptake and degradation of endocannabinoids by enzymes like fatty acid amide hydrolase (FAAH) for anandamide and monoacylglycerol lipase (MAGL) for 2-AG. Once broken down, endocannabinoids are recycled or excreted from the body.
G-protein
A GTP-binding protein that relays signals from a plasma membrane signal receptor, known as a G protein-coupled receptor, to other signal transduction proteins inside the cell Heterotrimeric G-Proteins - guanine nucleotide binding proteins 3 subunits Alpha, beta, gamma Alpha (Ga) - 15 subtypes (stimulatory Gas & inhibitory Gai) Beta (Gb) - 6 subtypes Gamma (Gg) - 12 subtypes Coupled with the cytosol terminal (GPCR) or not coupled Neurotransmitter binding changes conformation and alpha subunit exchanges guanosine diphosphate (GDP) for guanosine triphosphate (GTP) Different subunits have different affinities for different signaling proteins G-protein subunits typically define action
ionotropic receptors
Acetylcholine Glutamate GABA Glycine ligand-gated ion channels fast synaptic transmission
metabotropic receptors
Acetylcholine Glutamate GABA Serotonin Dopamine G protein coupled receptors (GPCRs) slower, longer lasting responses
adenosine receptors & caffeine
Caffeine causes most of its biological effects viaantagonizing all types of adenosine receptors(ARs): A1, A2A, A3, and A2B and, as doesadenosine, exerts effects on neurons and glialcells of all brain areas.
ligand-based GPCR signaling mechanism
Can activate different signaling pathways even when binding to the same ligand For the same receptor, using different neurotransmitters/synthetic drugs to activate them Use it for drug design Choose drugs that can activate the g-protein signaling pathways Beta-arrestin - shut down signaling of GPCRs
Advantages of photo-based approaches in neuroscience
Can control light Turn it on and turn it off, can control neuronal activity as you desire Accuracy Fast-switching "Less" side effects Targets only the specific cells/neurons in question Imaging friendly
glycine
Common inhibitory interneurons in spinal cord Produced from serine in presynaptic terminal Glycine is loaded into vesicles by VGAT Glycine hyperpolarizes neurons by opening chloride channels
GABA working mechanisms b/w neurons
Diffusion: GABA molecules diffuse across the synaptic cleft, which is the small gap between the presynaptic neuron and the postsynaptic neuron. GABA can also affect nearby neurons and glial cells in the vicinity.
luciferase
Enzyme-based approach Found in nature Fireflies: Photinus pyralis Sea Creature: Renilla reniformis Reaction releases energy in a form of light Using split-firefly luciferase reporter assay to study alpha-SYN oligomerization If there is an interaction between luciferase and the protein we are interested in, they will bond to each other If there is an aggregation, you can see fluorescence (light)
OptoXR
GCPR photo-based switch Receptor "conjugation" N-terminal of ChR2, C-terminal of GPCRs of interest Extracellular domain receiving the signal (light) Intracellular is recruiting signaling molecules Using this technique you can design any type of receptors and turn them on with light OptoXR in controlling reward behavior Injected this into reward circuit Three stages Stage 1: put mice in two area box and let them explore freely Stage 2: stimulate them with light when mice enter the right box Stage 3: let the mice explore 2 chambers freely, more likely explore the right chamber because their reward circuit associates this box with stimulation
criteria for a "good" drug
No medicine has only benefits or drawbacks Minimal side effects Safe Low chance of addiction High specificity Minimal withdrawal Not able to build up a tolerance Efficacy Dosing cost
LOV domain
Photoreceptor: AsLOV2 No binding partner Source organism: Avena sativa (oats) Mode of action: intramolecular conformational change Excitation wavelength: 450 nm Reversion wavelength: dark Excitation time: seconds Reversion time: tens of second In neuroscience research, attach protein to this photoreceptor
cryptochrome
Photoreceptor: CRY2 Binding partner: CIB1 Excitation wavelength: 450 nm Reversion wavelength: dark Excitation time: seconds Reversion time: minutes Source organism: Arabidopsis thaliana (flower)
G-protein cascade
Step 1 - Ligand binding Step 2 - G protein coupling & exchange GDP for GTP Step 3 - Gα and Gβγ trigger diverse signaling pathways via effectors Step 4- GTP hydrolysis through GTPase and inactivation of G protein Step 5 - reassembly of heterotrimeric G proteins
neurotransmitter criteria
Synthesis & storage in a presynaptic neuron Synthetic enzymes or genes expressed Released by presynaptic axon terminal Will mimic normal synaptic transmission when experimentally applied to postsynaptic neuron Inactivation mechanism Reuptake Recycling Breakdown Postsynaptic neuron has receptors for neurotransmitter Transmitter-gated ion channels G-protein coupled receptors
inverse agonist
a substance that binds to a receptor and produces the opposite effect of an agonist, reducing baseline or causing an inhibitory response.
antagonist
a substance that binds to a receptor without activating it, thereby blocking the action of agonists
partial agonist
a substance that binds to and activates a receptor but produces a submaximal response or effect compared to a full agonist
full agonist
a substance that binds to and activates a receptor, producing a maximum response or effect
GCaMP indicator
Three domains: M13 (N-terminal), calmodulin domain (C-terminal), GFP protein Different versions of GCaMP existing and utilized in neuroscience Slow versions (GCaMP6s), Fast versions GCaMP6f); jGCaMP7c exhibits greater fluorescence contrast Fast versions - respond fast in real time Slow versions - don't respond very fast No calcium = very dark Calcium release = trigger light release Red fluorescent proteins: jRCaMP1a and jRCaMP1b When calcium enters, the EGFP closes EGFP Can generate green fluorescent signals Found in nature, but use it in neuroscience research] Attach to GCaMP sensor molecules When calcium is present EGFP closes Calcium indicates neuronal activity, therefore the EGFP closes when the neuron is active Gives large variation of fluorescence between neurons example: NAc D1-MSN GCaMP response during hedonic feeding How we use GCaMP in neuroscience research AAV expression of GCaMP Behavioral correlation
G-protein subunits
Typical G-protein is divided into 3 types Control different proteins Gas = stimulates adenylyl cyclase and cAMP pathway Gai = inhibits adenylyl cyclase and cAMP pathway Gaq activates Phospholipase C (PLC-B) which in turn activates DAG and IP3 DAG leads to PKC activation and IP3 releases Ca2+ BUT Gβγ also can activate downstream secondary messengers! - most commonly open K+ channels = hyperpolarization
GPCR
Typical GPCR 7 Transmembrane spanning domains > 1,000 unique GPCRs Activation can lead to downstream opening of ion channel Activation of second messengers that increase Ca2+, signaling molecules like PKA, CAMKII, PKC, and /or affect gene transcription One long single polypeptide chain that crosses the membrane
Noradrenaline (norepinephrine)
alertness, arousal, memory, attention Catecholamine along with dopamine and epinephrine Using tyrosine as the precursor Digestion through monoamine oxidase & catechol-O-methyltransferase
three stages of addiction
binge/intoxication: individual consumes an intoxicating substance and experiences its rewarding effects withdrawal/negative affect: individual experiences a negative emotional state in the absence of the substance preoccupation/anticipation: one seeks substance again after a period of abstinence
addiction
cause harm to oneself or others the drug consumption is typically compulsive, frequent, and intense
serotonin
contributes to mood disorders sleep drug targets: SSRI's Using Tryptophan as precursor Multiple subtypes of receptors are identified SERT for recycling, target for anti-depressants
kappa opioid receptor (KOR)
dysphoria/depression
mu opiod receptors (MOR)
euphoric feelings
glutamate
excitatory neurotransmitter learning processes, synaptic plasticity, transmission of sensory info memory Mediates fast excitatory transmission Generated from glutamine (via glutaminase) Loaded into vesicles by VGLUTs, which are present only in glutamatergic cells Removed by neuronal and glial transporters: Excitatory Amino Acid Transporters (EAATs) Excess of glutamate can be dangerous and even produce cell death Abnormalities in EAATs lead to diseases: half of the cases of Amyotrophic Lateral Sclerosis (ALS) are caused by EAATs and cause degeneration of motor neurons
Neuropeptides criteria
large molecules composed of chains of amino acids (peptides) synthesized & released on-demand in response to specific signaling events-slower release neuromodulation terminated through enzymatic degradation no uptake mechanisms large dense core vesicles
dependence
mental desire of craving to achieve drugs effects. Hallmarks are tolerance and withdrawal symptoms
photocages
molecular drugs & neuropeptides modulate the drug responses in brain circuits as desired
3 primary opioid receptors
mu, kappa, delta
critical factors to consider when designing a drug study
objectives population sample randomization/blinding design administration/dosage duration of study safety
delta opioid receptor (DOR)
other mood changes (anxiety)
dopamine transporter, antiporter, & receptor
transporter: DAT antiporter: vesicular monoamine transporter (VMAT2) receptor: D1 or D2 receptors
GABA working mechanisms within neurons
presynaptic: Synthesis: GABA is synthesized within the presynaptic neuron from glutamate, another neurotransmitter. The enzyme glutamate decarboxylase (GAD) converts glutamate into GABA. Vesicular Packaging: Once synthesized, GABA is loaded into synaptic vesicles within the presynaptic neuron. This process is facilitated by the vesicular GABA transporter (VGAT), which exchanges GABA for protons (H+) inside the vesicles. Release: When an action potential reaches the presynaptic neuron, it triggers voltage-gated calcium channels to open. Calcium ions (Ca2+) enter the neuron, leading to the fusion of GABA-containing vesicles with the presynaptic membrane. This fusion allows GABA to be released into the synaptic cleft. postsynaptic Binding to Receptors: GABA binds to specific receptors on the postsynaptic neuron's membrane. The primary receptors for GABA are GABA-A receptors, which are ionotropic receptors. Ion Flow: Activation of GABA-A receptors leads to the opening of chloride ion (Cl-) channels. Chloride ions flow into the postsynaptic neuron. This influx of negatively charged chloride ions hyperpolarizes the neuron's membrane potential, making it more difficult for the neuron to reach the threshold for firing an action potential. Inhibition: The hyperpolarization caused by GABA binding to GABA-A receptors inhibits the postsynaptic neuron's excitability. In other words, GABA suppresses the neuron's ability to transmit signals to downstream neuron
GABA
primary inhibitory neurotransmitter responding to calmness relaxation prevents muscle contraction GABA (gamma-amino butyric acid) and glycine are two inhibitory neurotransmitters GABA is synthesized from glutamate by the enzyme Glutamic Acid Decarboxylase (GAD) in inhibitory neurons Blockade of GABA transmission induces seizures. GABA is loaded into vesicles by VGAT Removed from the synaptic cleft by transporters located on both neurons and glia: GAT-1, GAT-2, GAT-3. Enhanced GABAergic transmission is used to treat epilepsy Tiagabine(GABITRIL), blocks specifically GAT-1, enhances GABAergic transmission Vigabatrin(SABRIL), reduces the degradation of GABA by blocking the enzyme GABA amino transferase(GABA-T) There are two main type of GABA receptors: GABAA (ionotropic) and GABAB (metabotropic) GABAA receptor consists of a channel for Cl-
adrenaline transporter, antiporter, & receptor
receptor: beta or alpha adrenergic receptors reuptake by diffusing into the surrounding tissues and feedback mechanisms from the autonomic nervous system
DrBHP
red light switchable proteins Photoreceptor: DrBphP No binding partner Source organism: bacteria Mode of action: homodimerization, dissociation Can undergo a conformational change After excitation Excitation wavelength: 660 nm Reversion wavelength: 780 nm, dark
Acetylcholine (ACh)
used at the neuromuscular junction important in attention & memory processes muscle movements, cognition, memory, autonomic nervous system drug targets: nicotinic receptors, muscarinic receptors Precursor: Choline and Acetyl CoA by ChAT (choline acetyltransferase) Removed by Acetylcholinesterase Nicotinic Ach receptors - Ionotropic Muscarinic Ach receptors - GPCR Primary transmitter at Neuromuscular junctions The same neurotransmitter can have different postsynaptic actions, depending on what receptor it binds to