Final Objectives Flashcards
(113 cards)
1
Q
define “peptide” and contrast with “neuropeptide”
A
peptides - small proteins made up from amino acids that are joined by peptide bonds
neuropeptides are peptides that serve as NTs or hormones
2
Q
Compare and contrast the synthesis, storage and release of neuropeptides with those of the classical neurotransmitters
A
neuropeptides are encoded by genes - prepropeptides: regulated like any other protein in the body
- prepropeptide mRNA translocated to the ER: guided by signal peptide on pro
- signal peptidase chews peptide bond between prepropep and signal: creates propeptide
- propertied is released from the ribosome and goes trough post-translational modification - become the active neuropeptide
3
Q
Describe now N terminal acetylation and C terminal modifications can affect the activity of the neuropeptide
A
N-terminal acetyltransferases acetylate the N-terminal of the neuropeptide
- regulates its activity: can increase or decrease
C terminal modification
- PAM: admiration of glycine
4
Q
Describe the difficulties faces by neuropeptide pharmacologists regarding the design of selective agonist and antagonists for neuropeptide receptors
A
neuropeptides are flexible and have many random conformations
- they have to try each different confirmation to see which one is the right one
5
Q
discriminate between opiates and opioids
A
opiates: compounds purified from pure opium (poppies): morphine, codeine, and papaverine
opioid: any molecule exhibiting the properties of opiates
6
Q
Compare and contrast the three main classes of opiod peptides in terms of their precursors, and receptor preferences
A
BETA ENDORPHINS - precursor: POMC - receptor pref: mu > delta > kappa ENKEPHALINS - precursor: proenkephalin - receptor pref: delta > mu > kappa DYNORPHINS - precursor: prodynoprhins - receptor pref: kappa > delta > mu
7
Q
Describe the major intracellular signaling pathway used by opioid receptors
A
opioid receptors - G protein coupled - 7 transmembrane spanning regions
Driven by Gi activation
- inhibits AC - inhibits Na influx and NT release
- opens K channels: hypo polar
- inhibits Ca channels: decreases Ca entry - inhibits NT release
8
Q
Describe the mechanisms of action of morphine, heroin, oxycodone, codeine etc and explain how these drugs impact addition by affecting dopamine transmission in the nucleus accumbens
A
Mu opioid receptors (MOR)
- subtypes 1 & 2
- beta endorphin: higher affinity
MOR activation produced effect similar to DOR
- analgesia, euphoria
- blood pressure, gastrointestinal
when opioids are bound to MOR on GABA neuron, it inhibits GABA release
- decreases GABA R activation on postsynaptic cleft - no longer inhibits DA
9
Q
explain how affecting dopamine release in the nucleus accumbens, kappa agonists might lead to dysphoria
A
KOR - dynorphin has high K affinity
dynorphin-secreeting neuron in NA becomes sensitized after long-time cocaine/amphetamine usage
- release of dynorphin stimulates presynaptic kappa receptors in DA neurons: inhibits DA release
10
Q
Define “growth factors” and contrast with “neurotrophin”
A
growth factors - proteins that simulate cellular proliferation and promote cell survival
neurotrophins - growth factors that act exclusively in the nervous system
11
Q
Describe the intracellular signaling cascade(s) activated by the stimulation or Trk receptors
A
bind to the TRK family of RTKs - stimulate MAPK pathways
TRK - limited to neurons
- kind domains conserved, differ in extracellular domains
12
Q
Describe how acetylcholamine is synthesized from the precursors acetyl CoA. What enzyme is involved?
A
cholineacetyltransferse (ChAT) - swaps the CoA of acetyl CoA with a choline molecule
- condensation reaction
synthesized in the cytoplasm
- acetyl CoA transformed into citrate to pass through mitochondrial membrane using carnitine transport
13
Q
Describe the sources of acetyl CoA and choline used for ACh synthesis
A
acetyl CoA - glycolysis by product
- synthesized in the mitochondria
choline - found in diet
- egg yolks, seeds, veggies: broken down in liver
- can cross BBB
- transport systems of neuron: high affinity: Na dependent pump, low affinity: diffusion
14
Q
describe the rate limiting factors of ACh
A
rate limiting factor in ACh synthesis is the rate of the choline high affinity uptake - sodium dependent transport pump
15
Q
Describe how depolarization of cholinergic neurons leads to the release of ACh
A
VAChT - vesicles for ACh storage/release at axon terminals
- after newly stored ACh is released, there is a reserve pool of ACh for long stimulation
16
Q
What are the proteins involved in ACh release?
A
proteins that help fuse the vesicle to the membrane:
- synapsin I: draws vesicles to the membrane
- synaptotagmin, synaptophysin, and synaptobrevin are involved in fusion and release
when AP fires - [Ca] increase - synaptotagmin and synapsin draw vesicle to membrane - SNARE complex fuses and releases ACh
17
Q
explain the role of acetylcholinesterase (AChE) intermitting ACh activity. What are the factors that regulate it?
A
AChE - hydrolyzes acetylcholine into acetate and choline
- stops transmission
- very efficient: 50000 ACh/enzyme/sec
- inhibited by high [ACh]
choline is transported back into the terminal, acetate diffuses away
18
Q
describe the 4 main centers of cholinergic cells in the brain and their connectivity
A
- Striatal complex (CNS)
- cholinergic interneurons
- input: glutamate and DA
- output: extrapyramidal motor system, reward pathways - Basal forebrain
- cholinergic projection neurons
- input: lots
- output: hippo and cortex - Diencephalon - projections to the interpeduncular nucleus
- Pontomesencephalon - projections to subcortical areas
19
Q
Describe the role of ACh in the peripheral motor system and the autonomic nervous system
A
peripheral motor: ACh found in all neuromuscular junctions, cause muscle contractions
ANS
- primary transmitted or preganglionic fibers (para and sympathetic)
- released by parasympathetic postganglionic fibers
20
Q
Describe nicotinic receptors in terms of its effector systems and distribution
A
ionotropic: excitatory
muscle type nAChRs are located at neuromuscular junctions:
- electrical impulse from neuron signals muscle contraction
neuronal nAChRs - located between neurons in the CNS
- important for cognitive function, learning and memory, arousal, reward, motor ctrl and analgesia
21
Q
Describe muscarinic receptors in terms of their effector systems and distribution
A
G-protein coupled receptor
- M1,3,5 - Gq
- M2,4 - Gi
involved in many physiological functions: HR & force, contraction of smooth muscle, release of NTs
22
Q
Explain the structure of the nicotinic receptor and how it can give rise to at least 9 different types
A
pentramic membrane protein (like all other ion channels)
- 4 transmembrane polypeptide chains (a b g d) : different combos give different subtypes
- subunits cross membrane - create pore
activation: ACh binds to alpha subunit - causes conformation change - allows passage of cations
23
Q
Describe the anatomical and psychophamalogical evidence for a role of nicotine in cognition
A
- activation of basal forebrain (ACh center of brain) increases behavioral performance in mice
- Alzheimer’s damages cholinergic neurons in BF: cognitive performance decreases
- nicotine patches increase cognitive f(x) in Alzheimer’s patients
- nicotine receptor antagonist impair working memory
- cucare: arrow poison used by South Americans to paralyze prey - nicotinic R antagonist
24
Q
Describe how we can prove that amino acids act as NTs
A
glutamate, aspartate, non essential amino acids meet requirements for NTs
25
What are the requirements for something to be considered a NT?
1. must be concentrated at neurons
2. released upon neuronal stimulation
3. activate receptors to produce a biological event
26
Describe the major glutamate pathways in the brain
- descending pathway from cortical pyramidal cells
- descending pathway from the cerebellum
- interconnections of limpid system (amygdala + hippo)
- descending pathways down spinal cord
27
Describe the function of transaminase, glutamine synthase, glutaminase and SN1 in the synthesis and recycling of glutamate in the brain
transaminase: converts glutamate, aspartate, glutamine, and alpha-oxoglutarate/ketoglutarate into each other
glutaminase: converts glutamine into glutamate
glutamine synthase: converts glutamate into glutamine
- glutamine is transported out of non-neuronal cells using SN1 (Na/H pump)
28
Describe the function of EAATs and list the major EAATs round in glia vs neurons
Excitatory amino acid transporters (EAATS)
- reuptake glutamate from the synapses/extracellular space
- coupled to electrochemical gradient for Na, K, and H: translocates glutamate and aspartate against [gradient]
- critical for regulating extracellular levels of glutamate
- EAAT 1/2 - glia
- EAAT 3 - neurons
29
Identify the 3 major ionotropic glutamate receptors and explain how they differ in terms of cation conductance
NMDA - permeable to Ca the most, some Na and K
- 2 subunits: GluN1,2,3
- N1: obligatory unit
- N2: glu binding site
- Mg blocks the pore at rest
AMPA/Kainate - depends if AMPA has functional GluA2 with Arginine (R): positively charged, will repel; calcium
- 4 subunits: GluR/A(1-4)
- R1: obligatory unit
- If GluA2 missing or glutamine (Q) not switched with arginine (R) - Ca can flow through
30
Explain why the AMPA component of a glutamate-induced EPSC is short in onset and decay, while the NMDA component is longer in onset and decay
AMPA is just a ligand receptor sensitive to glutamate
NMDA component is longer because there is an Mg block
- Mg block present when the cell is negatively charged
- requires that the cell depolarizes before Mg leaves
Use opposite antagonist to see the relative roles during EPSC
31
Explain how the multiplicity of AMPA receptors arises in the brain
AMPA receptors have "flip" and "flop" splice variants in the domain
- different conformations - depends on what happens during splicing
- affects closing
- flip out, flop in
32
Describe the structure of the NMDA receptor in terms of its major binding sites
GluN2: glutamate binding site
glycine site - co-agonist: necessary for channel opening
PCP site: somewhat voltage dependent, within channel
- ketamine can bind as noncompetitive antagonist
Alcohol site: inside channel, inhibits
Voltage-dependent Mg binding site: blocked by other divalent cations, depends on the type of GluN2 subtype
33
Describe the role for the NR1 vs NR2 subunits in NMDA receptor function
NR1 - obligatory site of the receptor: must be there for the receptor channel to open
NR2- subunit where glutamate binds
- N2B: high affinity, slow desensitization: drugs of abuse up regulate GluN2B in adults
34
Explain how Ca entry through NMDA receptor leads to receptor inactivation
Ca can activate calcineurin
- PP that removes phosphate from the receptor: contributes to channel closing
Ca can bind with calmodulin
- interacts with GluN1 - reduces open frequency
- direct effect that's kinase independent
35
explain why the NMDA receptor channel is closed at rest and what are the requirements for channel opening
closed at rest because there is an Mg molecule blocking the pore
- Mg is bound when the cell is negatively charged
- release of Mg occurs when the cell is depolarized
36
Explain how non-competitive NMDA antagonists influence channel function
non-competitive NMDA antagonists bind to allosteric sites
PCP site - inside the channel: blocks the channel so opens can't get in
- binds PCP, ketamine, alcohol
- when people experience withdrawal from these drugs, it induces massive up regulation in NMDA receptor expression: need more NMDA receptors bc there weren't many in use before
37
Explain how D-cycloserine may serve as an effective adjunct therapy for treating schizophrenia
D-cycloserine - partial agonist of the glycine binding site
| - opens more channels in patients with schizo
38
Explain the role AMPA receptors in NMDA receptor function
AMPA can depolarize the cell, which helps remove the Mg block in NMDA receptors and allow the channel to open
39
Explain the general importance of postsynaptic scaffolding molecules for regulating normal glutamate transmission through receptors
Scaffolding proteins regulate trafficking and cluttering at the membrane
- controls receptor cross talk: can help/prevent protein signaling by changing relative location
Group 1 mGluRs rely on homer - keeps metabotropic proteins close
- regulates ability to stimulate voltage-gated ion channels
40
List the 3 catecholamine NTs in our brain and describe the hallmark chemical features of catecholamine NTs
all synthesized from tyrosine
- actively transported across BBB
- contains CATECHOL nucleus and and ethylene group
three catecholamines: dopamine, norepinephrine, epinephrine
41
Outline the synthetic pathway for dopamine, norepinephrine, and epinephrine including all enzymes involved
DA synthesis
1. Tyrosine hydroxylase (TH) takes tyrosine and makes DOPA
- RATE LIMITING STEP - occurs at nerve terminals
2. AADC - makes dopa into dopamine
- located in DA neurons
- requires B6 derivative
NE synthesis
4. DBH - DA beta hydroxylase: catalyzes DA to NE
- located in NE neurons
- vitamin C cofactor
E synthesis
4. PMNT - converts NE into E: requires methyl donor
- located in medulla and brainstem
42
Explain why an increase in dietary tyrosine does not result in more catecholamine synthesis, but administration of L-DOPA can
rate limiting step of catecholamine synthesis is the transformation of tyrosine into DOPA by TH
- adding anything after this step could increase catecholamine synthesis
43
Point out which enzyme in catecholamine synthesis and describe the means through which this enzyme is regulated in the short and long term
TH - rate limiting step
SHORT TERM
- gene regulation
- phosphorylation by PKA, Ca, CAMKII, PKC and de-P @ serine residues: reduces end product feedback
LONG TERM
- transcriptional regulation of TH gene by extracellular stimuli
- transcriptional gene: TH promoter contains several regulatory elements
44
Describe how DA and NE are packaged into vesicles and explain how reserpine affects NT levels
DA - stored in vesicles by VMAT (vesicular monoamine transporter)
- uses electrochemical gradient generate by H-ATPase pump to get into vesicle
RESERPINE - blocks VMAT
- temporary increase in NT levels in cytoplasm: can diffuse into synapse
- decrease in NT packaged in vesicles
NE
- vesicles contain DBH that convert DA to NE
- synthesis in cytoplasm and in vesicles: transported by VMAT
45
Define varicosities and explain how release catecholamines from terminals differ from amino acid NTs
varicosities - bundles of vesicles contain catecholamines on the axon
- NON DIRECATIONAL/MODULATROY RELEASE: more widespread
- other NTs usually released at synapse
- vesicles docked close to active zone: require less calcium
46
Describe the catecholamine transporters and how they affect signaling
catecholamine transporters - important for reuptake
- DAT/NET move NT from synapse into the cytoplasm of presynaptic terminal: reloaded by VMAT or broken down by MAO
affects signaling:
- limits duration of pre/postsynaptic activation
- limits diffusion of NR molecules to other synapses
- permits recycling and reuse of unmetabolized transmitters
47
Compare and contrast the mechanisms of action of cocaine and amphetamine vis-à-vis the catecholamine transporters
Cocaine: non-selective reuptake inhibitor
- binds to DAT, NET, and SERT: blocks transporter reuptake after vesicle release
- inhibits DAT, MAOI
Amphetamines: disrupts action of VMAT to cause leakage of NT out of vesicles
- cause cytoplasmic levels of NT to rise: triggers reverse transport of NT
- enters through VMAT, disrupts pH of vesicle: drive DA/NE out into the cytosol and block TH
48
Compare and contrast MAO-A and MAO-B, highlighting major inhibitors
MAO-A: almost exclusively in NE neurons
- preferential enzyme for NE, E, and 5-HT
MAO-B: almost exclusively for 5-HT neurons
- involved in DA metabolism
MAO-inhibitors: prevents metabolism
- suicide substrates: used to be irreversible
- increase NT in tissue and synapse: treats OCD, depression
49
Explain how genetic variance in COMT might affect DA and NE levels within the PFC
COMT - responsible for fraction of NT breakdown
genetic variance:
- val/val - more COMT activity leads to 40% more NT breakdown
- deletion syndrome - 1 copy of COMT
- if one contains Met: poorer COMT function: causes excessive NT - ADHD
50
Describe the origins and projections of the major DA and NE pathways in the brain
DA pathways
- substantia nigra (SNc): dorsal striatum - role in learning and execution of motor programs
- ventral tegmental area (VTA): hippo, amygdala, PFC and cingulate cortex - role in motivation, reward behavior, attention
NE pathway
- produced in pons/medulla
- projects to the locus coeruleus (survival behaviors) and amygdala (enhanced memory for stimuli)
51
describe the classification of DA receptors into D1-like ad D2-like families based on intracellular signaling cascades
```
D1-like: D1, 5
- Gs coupled receptors: TF = CREB
- post-synaptic side
D2-like: D2, 3, 4
- Gi coupled receptors
- 2/3: presynaptic side
```
52
Describe the classification of adrenergic receptors based on intracellular signaling cascades
```
adrenergic: important for NE and E
alpha
- a1 - postsynaptic: Gq - stimulatory
- a2 - presynaptic (clonidine): Gi - inhibitory
beta - post synaptic
- Gs - stimulatory (lungs vs heart)
```
53
Describe the clearance of DA from the synapse as well as the enzymatic deactivation of the NT
uptakes by DAT back into the presynaptic terminal
- repackaged into vesicles by VMAT
- degraded by MAOB (90% - cytosolic) of COMT (10% - cleft)
54
Describe the role of D2/3 and alpha 2 receptors in regulating NT release
D2/D3 - presynaptic DA autoreceptors
Alpha 2 - presynaptic NE/E autoreceptor
both Gi, inhibit further release, and are located on the outer edges of the active zone
55
Distinguish between D1 and D2 receptors in terms of their cellular location
D1 - located in every brain region except GP, SN, VTA
| D2 - located in every brain region besides GP
56
Describe the pathway for DA or NE receptor internalization upon stimulation
G protein receptor kinases (GRK): when NT is occupying receptor, GRK can come and P-ate the receptor - triggers internalization
- arrestin binds to the P'd receptor and dissociated G protein: assocated with clatharin coated pits - dyamin mediated invagination
- internalized in vesicle: acidification by protein pum
- changed conformation, triggers NT release
- dephosphorylated and recycled
57
Explain derivation of the name serotonin
isolate from the blood, induced muscle contractions in the heart
heart: serum + tone = serotonin
58
describe the chemical features and distinguish it from catecholamines
contain indole group: derived from tryptophan
| catecholamine - catechol group
59
describe the two general 5-HT systems in the brain in terms of their projections
```
caudal System
- B1-4 (cell bodies): pons and medulla
- projects down spinal cord
- important in sensory, motor and autonomic f(x)ing
Rostral system
- B5-9 - dorsal and medial raphe
- 6-8 provide forebrain 80% of 5-HT
- innervate cortex, basal ganglia, habenula, thalamus, hypothalamus, limbic system
```
60
Distinguish between the projections of the D and M ascending 5-HT systems based on morphology and sensitivity to toxins
D - dorsal raphe
- thin, very numerous fibers in the brain
- many varicosities: widespread effects on fontal cortex and stratal structures
- more vulnerable to toxins
M - medial raphe system
- thick, large varicosities
- more conventional synaptic connections - hippo and septum
61
Outline pathway through which 5-HT is synthesized
1. Tryptophan hydroxylase (TH) converts tryptophan into 5-hydroxytryptophan
- RATE LIMITING, in cell body
2. AADC (same as DA) takes 5-hydroxytryptophan and makes 5-HT
62
What regulates the synthesis of 5-HT?
regulated by PKA, CaMKII - both phosphorylate to regulate
gene regulation by cAMP/CREB, but no CRE site
no end product feedback
PCPA - irreversible antagonist on TH
63
Describe the mechanism of action of reserpine and how it affects 5-HT transmission
blocks VMAT - in charge of uptake into vesicles (uses H gradient)
- blocked VMAT depletes 5-HT stores
64
Describe the mechanism of action of fluoxetine, paroxetine, and sertaline and how it affects 5-HT transmission
selective serotonin reuptake inhibitors (SSRI) - bind to the transporter and blocks reuptake
varying affinities - lower Ki = higher affinity
65
Explain the effects of agonist and antagonists at 5-HT1A and or the 5-HT1B/D receptors upon extracellular levels of 5-HT
1A - located on cell body
1B/D - located on presynaptic terminal
Gi coupled 5-HT auto receptor: prevents further release of 5-HT
66
Describe the intracellular signaling pathway for 5-HT2 receptors and relate this to their hallucinogenic profile
Gq activated: increase PI and Ca signaling
| - can stimulate other pathways producing hallucinogenic experience
67
Distinguish 5-HT3 receptors for other 5-HT receptors in terms of structure, function, and localization in brain
cationic Na channels: only ionotropic 5-HT receptor
- low expression in brain, high in postrema
- low BBB specificity
potential to regulate affective, cognitive and motivational disorders
- can cause nausea
68
describe heteroreceptor. describe the relationship of the 5-HT heteroreceptor and psychosis
heteroreceptor formed by 5-HT2A (Gq) and mGluR2 (Gi)
- in normal balance, Gi is activated more
- psychedelics cause the balance to shift to more Gq dominant - more stimulation
69
Compare and contrast the purines adenine and guanine with purinergic NTs adenosine and ATP
purinergic transmitters - nucleoside and nucleotide derivatives of purine bases
- adenosine: change the number of phosphate groups between two adenine molecules - Ap#A
- ATP - adenosine with 3 phosphates: adenosine kindness add P's to make ATP in cells
70
Compare and contrast the function of ATP synthase and ATPase
ATP synthase: makes ATP in the mitochondria
- add P to ADP
ATPase - makes ADP: removes P from ATP
71
List the major types of purniergic NTs and compare and contrast their mechanisms of storage and release
```
Ap#A and ATP: stored in small synaptic vesicles and release in response to APs (Ca dependent)
often co-localized with classical NTs
VNUT - packages ATP for release
VACC - channel for ATP release
ENT/CNT brings adenosine back into cell
```
72
Compare and contrast the 2 major types of nucleoside transporters
equilibrate nucleoside transporers (ENT 1-4)
- bidirectional
- mediates the majority of adenosine uptake
concentrative nucleoside transporters (CNT 1-3)
- mediate Na dependent influx - concentrates adenosine in cells
73
Explain how ATP release can result in the generation of the NT adenosine
after ATP is released, enzymes called ectornucleoridases can metabolize into adenosine
- ectodiphosphohyderolase and 5'-NT (into Ado)
- makes ATP a possible source of extracellular adenosine
74
Compare and contrast the 3 major subtypes of purinergic receptors and indicated when are most concentrated in the brain
P1 - adenosine receptor - G protein coupled
- A1: Gi/o- highest expression in CNS: sedation and anxiolysis
P2Y - Gq coupled
- substrate specificity: binds purine pyrimidine, nucleotide di and triphosphates, and Ap#A
- like to dimerize
P2X - ATP-gated cation channels
- rapid Na, K, and Ca influx causes membrane polarized
- found in neuromuscular junction and brain (X4)
75
Explain the mechanism of action of caffeine
blocks the P1A1 receptor
- highest expression in CNA
- highest affinity for adenosine activation
- sleepy receptor
76
Explain how adenosine is predicted to be neuroprotective but explain a drawback to adenosine therapy for treating ischemia
ischemia induces oversimulation of Glutamate receptors - excitotoxicity
- adenosine accumulation: transported out of cell by ENT
- some P1A1 receptors are located on presynaptic side of glutamate neurons - inhibit when activated
problems: can activate P1A2 (Gs coupled) predicted to promote toxicity
77
Explain the two major ways in which A2A and D2 receptors interact to influence intracellular signaling
A2A (Gs) are highly concentrated in stratal structures
- colocalized with D2 Da receptors
- activation - stimulates cAMP (inhibited by D2)
- agonists inhibit D2 stimulated behaviors
- forms heterodimer with D2
78
Explain how the application of ATP can induce pain
extracellular ATP suggests cell damage
applying ATP to human skin causes acute pain
P2X are found in sensory neurons in dorsal root ganglia and nociceptive nerve terminals
- contribute to neuropathic and inflammatory pain
79
From what does the name endocannabinoids derive
endo - endogenous
| cannabinoid - everything that resembles cannabis (marijuana)
80
what are the two different subtypes of endocannabinoids
2-AG and anandamide (AEA)
81
Describe the synthesis and degradation of 2-AG
synthesized from lipid precursors from the plasma membrane
- PI derivative: PLC beta (Gq activation) takes PI, and with Ca, makes DAG
- DAG lipase turns DAG into 2-AG
Degradation: monoacylglycerol lipase (MGL) takes 2-AG and makes arachidonic acid + glycerol
82
Describe the synthesis san degradation of anandamide (AEA)
synthesized from lipid precursors from the plasma membrane
- PE (phosphatidylethanolamine) derivatve
- N-acyltransferase + Ca takes Pe and makes it into N-arachinodonyl PE
- PLD - takes N-arachidonoyl PE and makes it into anandamide
degradation: fatty acid amide hydrolase (FAAH) takes anandamide and makes arachidonic acid and ethanolamine
83
Define retrograde messenger and explain how endocannabinoids function to inhibit presynaptic activity
retrograde messenger 0 created in the postsynaptic terminal and signal to the presynaptic terminal
- 2-AG and anadamines are both retrograde messengers
- bind to presynaptic CB1 receptors and inhibit presynaptic activity (also the target of THC)
- can diffuse across membrane bc its fatty
84
Compare and contrast the two different endocannabinoid receptors in terms of their location, homology, and what other pathways they effect
CB1 - found in every brain region
- target of THC
- primarily on presynaptic terminals of excitatory/inhibitory neurons: heterosexual inhibition of glutamate an GABA release
CB2 - found primarily in immune cells: target for medicinal cannabis
BOTH Gi/o coupled
- inhibitory signal: downers, generally relaxes nervous system
- also found in terminals of other neurons
85
describe the effect of chronic cannabis use on receptor expression
chronic expression of cannabis on its receptor results in its down regulation
- overstimulate - back down receptor: reduction in CB1R binding
- can change receptor levels and power of CB1R to control [GABA] and [glutamate]
86
Describe the rumination of endocannabinoid signaling
Transport:
- can diffuse passively through membranes
- but transport is facilitated by endocannabinoid transporters: energy independent
Hydrolysis:
- FAAH for anandamide into arachidonic acid + ethanolamine
- MGL - 2-AG into arachidonic acid + glycerol
87
Summarize the therapeutic potential of agonists at CB1 receptors and FAAH/MGL inhibitors
CB1 agonist
- stimulation reduces nausea
- stimulation of feeding
- stimulation is analgesic: agonist reduced neuropathic and inflammatory pain
FAAH and MGL inhibitors: promotes actions of endocannabinoids on CB1 receptors
- pro-appetite, analgesics and antidepressant
- combo with DA agonist improves motor f(x) in Parkinsons
- advantage: enzyme antagonist would exert effects only at active synapse - NT synthesizes on an as needed basis
88
Describe the structure of the 2 major gaseous NTs
```
nitrous oxide (NO) - non polar double bond
- 7 electrons on the nitrogen: extremely reactive free radical
carbon monoxide (CO): polar triple bond
```
89
Explain the beneficial effects of NO supplements or other dietary supplements that lead to an increased production of NO
causes smooth muscle to relax
- acts as vasodilator: help with BP
- acts as bronchodilator: help with BP and working out
- stops blood platelet cells from forming clots
- controls action of every orifice
- helps immune system fight infections and tumors
- mediation in inflammation and rheumatism
- penile erections
- TRANSMITS MESSAGES between nerve cells: associated with learning, memory, sleep, pain sensation
90
List 3 enzymes involved in NO and CO synthesis
NOS - NO synthase has 3 isoforms:
nNOS - exclusively in neurons
- NO released from neuron upon stimulation of nNOS in response to NMDA activation
- converts arginine to NO
eNOS - endothelial NOS
iNOS - immune cells
all found in neurons
Heme oxygenase (HO) - generates CO in neurons
- 3 isoforms: HO1-3
- HO2 enriched in neurons: degrades heme to biliverdin, iron and CO
91
Describe the synthesis for NO and outline the role of NMDA receptors in this regard
nNOS
- NMDA receptor activation: channel opens, Ca comes into the cell
- nNOS binded to NMDA-scaffolding protein PSD-95
- nNOS activated by Ca-calmodulin binding: converts Arginine into NO
- NO freely diffuses out of neurons: simulates GC - formation of cGMP - PKG activation
- cGMP broken down by PDE-5
92
Describe the way in which CO and NO meet the criterion for a NT and what features make them atypical
no reuptake, package, storage, released when synthesized
| made in neurons
93
Explain how excessive glutamate release can lead to neurotoxicity via stimulation of NO
NO can react with oxygen to produce reactive oxygen species: toxic to neurons
- observed in stroke and other states of hyper glutamatergia
NO can s-nirtrosylate cysteine residues on proteins
- alter function of signaling enzymes, g proteins, ion channels
- high Ca - apoptosis
94
explain why the activation of the NMDA receptor but not other Ca channels leads to stimulation of NO
nNOS is attached to NMDA-scaffolding protein PSD-95
| - proximity allows for stimulation
95
Explain how dietary supplements containing both arginine and citrulline would result in greater NO production than arginine alone and describe the possible negative consequences of overdosing
arginine and citrulline are recycled into each other
- NO = byproduct when arginine is transported into sitrulline
- can have too much NO in the body
96
Explain how alterations in CAPRON levels can influence NMDA receptor-mediated neurotoxicity
CAPRON - protein bound to the density
- carboxyl terminal PDZ ligand of nNOS that prevents ability to associate with PSD-95
- NO nitrosylates protein on CAPRON
97
Describe synthesis pathway for CO and outline role for Group1 mGluRs in this regard
Heme oxygenase (HO) degrades heme into biliverdin, iron and co
- CO freely diffuses out of neurons: stimulates GC
- regulation not well understood, maybe PKC
- activation of Gq receptors -- Group 1 mGluRs
- lead to direct activation of HO2 by casein kinase 2 (CK2) or Ca/calmodulin kinase
98
Describe the enzymes and processes involved in synthesis and breakdown of GABA
synthesis
- Glutamate decarboxylase (GAD) converts glutamate to GABA
- promoted cycle of holoenzyme (active form) to apoenzyme (inactive) by dissociating necessary cofactors
- GABA is a competitive inhibitor of glutamate binding site on GAD: negative feedback control of GABA synthesis
Degradation: GABA-T - aminotransferase - transfers amino group of GABA to
- mitochondrial enzyme
- alpha-ketoglutarate
- products are succinic semialdehyde and glutamate
99
Explain how the synthesis of GABA depends upon the synthesis of glutamate
GABA is dependent on glutamate synthesis because glutamate is the precursor to GABA
100
Trace the entire pathway from glutamate synthesis to GABA
glutamate
- glutamate, aspartate, glutamine, alpha-oxoglutarate, alpha ketoglutarate converted by transaminases to form each other
- glutamine is converted to glutamate by glutaminase
glutamate transformed into GABA by GAD
101
Describe the mechanism of action of Vigabatrin and how it might affect seizure threshold
GABA-T inhibitor
- inhibits GABA breakdown
- decreases seizure threshold
102
Describe what GAT is for GABA
reuptake of GABA
1/3 are high affinity
- bidirectional: AP will actually induce GABA release into synapse
Na/Cl dependent
103
Describe the mechanism of action of benzodiazepines and how they might affect seizure threshold
GABA A agonist
- Anxiolic, relaxing and sleep inducing
- shifts Kd for GABA with out affecting Bmax
- BDS receptor has allosteric interaction with GABA site - increases probability of channel opening
104
describe the mechanism of action of barbiturates and describe how they might affect seizure threshold
- sedative, relaxing and sleep inducing
- increases duration of channel opening
- enhances GABA binding to GABA Site and Bz to BZ site
105
Describe GABA a recetpors
ionotropic Cl channel
- agonist - intoxication and LSD like effects
- antagonist - proconvulsant
106
Describe GABA B receptors
Gi coupled metabotropic receptors
- inhibition of AC, increase K conductance, inhibits Ca conductance
function:
- auto inhibition of GABA terminals
- heteroinhibiton of other neurons (glutamate)
107
Why are there 850 possible different types of GABA A receptors
6 alpha, 4 beta, 3 gamma, 1 delta isoforms
2 alpha, 2 beta, 1 gamma/delta novel subunits
Lots of possible subunit combos
108
Explain how agonists on the BZD site influence GABA A function
BZD site - GABA A co-agonist: anxiolytic
- relaxing and sleep inducing drugs
- shifts Kd for GABA without affecting Bmax
- increases probability of GABA channel opening
109
Explain how agonists at the barbiturate site influence GABA A function and pharmacology
Barbituates - GABA A co agonist: sedative
- sedative-hypnotic drugs
- increase duration of channel opening
- increases GABA binding to GABA site, BZ binding to BZ site
110
Explain how GABA A subunit composition influences the affinity and binding specificity for various agonists
BZD binding requires the gamma 2 subunit
| alcohol has more potent effect with delta subunit
111
Describe the effect ethanol has on GABA receptors and its proposed binding mechanism
ethanol enhances Cl- conductance
- must already be open and active for alcohol to elicit a response
- more potent with delta subunit
- interacts with residues on M2 domain
112
Describe the evidence that neurosteroids regulate GABA A function
exhibit sedative-hypnotic effects
- progesterone and cortisol metabolites: stimulate Cl uptake, increase Bz binding
other steroids: inhibit GABA A receptor function - proconvulsant
113
Describe the proposed GABA C receptor
Structurally similar to GABA A
GABA C
- composed of rho elements only
- expressed in retina
- not modulated by Bz, barbiturates, neurosteroids
- slow and sustained response to agonist (GABA A - quick)
