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Physiology and Pharmacology > Pharmacology I-IV > Flashcards

Pharmacology I-IV Flashcards

1
Q

Langley’s experiment : giving rise to idea of receptors

A

1) pilocarpine added to heart - slows heart rate and increases savliva secretion
2) if atropine added to heart - nothing happened
3) atropine + pilocarpine - pilo didnt slow heart rate
= effects were antagonised by atropine
effects dependant on concentration of poison and affinity for substances

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2
Q

Experiments with nicotine and curare on chicken legs

A 
Action --- Contraction?
stimulate nerve --- yes
apply nicotine --- yes
apply curare and stimulate nerve --- no
apply nicotine and curare --- no
= SO NICOTINE MIMICS EFFECTS OF STIMULATION, CURARE STOPS BOTH,
DOES IT ACT ON NERVE OR MUSCLE?:
DENERVATE (kill nerves)
apply nicotine --- yes
apply curare and nicotine --- yes
=  SO NICOTINE AND CURARE ARE ACTING ON MUSCLE, STIMULATING NERVES PRODUCES SUBSTANCE THAT MIMICS ACTION OF NICOTINE
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3
Q

Ehrlich’s experiment

A

on blood cells - found evidence of receptors:

applied dyes to cells and saw different cells absorbed different dyes - selectivley

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4
Q

Macromolecular proteins

A

serve as recognition sites for neurotramsitters, hormones etc used in cell communication
also refers to any protein of a cell that can bind a molecule/drug, which modulates some activity

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5
Q

Chemical mediator

A

extracellular signalling molecules e.g. hormones

detected by target cells through receptors

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6
Q

cell signalling occurs when …

A

receptors detect extra cell signals and genterate intra cell signals = signal transduction

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7
Q

Endocrine communication

A

long distance
sig mol secreted into blood stream
e.g. adrenaline, insulin

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8
Q

Paracrine communication

A

locally, signals to neighbouring cells
may be stored in vesicles or synthesised on demand and diffuse across membrane
if cell receiving is same type as cell making it = autocrine
e.g. growth factors : histamine, nitric oxide, anadin, CBD

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9
Q

Neuronal communication

A

may be long distance, very fast, specific to target cell (synapses)
chemical mediators that diffuse across cleft from vesicles
e.g. botox - interfere with synthesis, storage or release of neurotransmitters; nicotine and curare - act on receptors for neurotransmitters

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10
Q

Contact - dependant communication

A

shortest range
used in immune system
e.g. T cell receptors interact with receptors on antigen presenting cells to become activated, so they can recognise infected/damaged cells, CAR-T immunotherapy uses contact dependant to kill cancer

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11
Q

Bioassays =

A

experimental assays, concentration of substances measured by the biological response it produces

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12
Q

Bioassays used to:

A

measure pharmalogical activity of new substrates
investigate function of endogenous mediators
measure drug toxicity and unwanted effects

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13
Q

Loewi’s experiment - followed on from Langley

A

if vagus was stimulated, heart rate slowed - what caused this?
if it was a chemical, he should be able to collect it and test it on another heart:
2 isolated hearts, stimulated 1 vagus nerve and collected medium heart was in
put the medium onto 2nd heart and the message transferred - he called it ‘vagustoff’
Dale continued this research on leeches and found the chemical was Ach

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14
Q

Acetylcholine effects on differenct receptors (CNS)

A

Somatic efferent system = binds to nic receptors and controls skeletal muscle
sympathetic system =
nicotinic - noradrenaline - blood vessels
nicotinic - muscarinic - sweat glands
nicotinic - adrenal medulla
Parasympathetic system = nicotinic - muscarinic - salviary glands

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15
Q

Experimental criteria:

A

1) released from cells in sufficient amounts to produce bio action on target in appropriate time frame
2) application of authentic sample of mediator reproduces original bio effect
3) interference with synthesis, release or action (e.g. enzyme inhibitors) abalates or modulates original bio effects

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16
Q

Synthesis of small molecules

A
  • regulated by specfic enzymes, peptides synthesis regulated by transcription - which mediator produced depends on which enzymes/gens are active
  • some secretory vesicles store more than one type of transmitter
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17
Q

Synthesis, storage and release

2 groups:

A

1) mediators that are preformed are stored in vesicles then released by exocytosis = allows for rapid communication (microseconds)
2) mediators produced on demand are released by diffusion or constitutive secretion = take longer to act (minutes to hours) e.g. lipids and small gases

in nerve ending, transporter protein loads neurotransmitters into vesicle
vesicle docks at plasma membrane
when signal is generated e.g. action potential, vesicle fuses with membrane creating fusion pore
neurot escapes and goes to receptor on other cells
endocytosis recycles vesicle

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18
Q

Research into mediators

A

neurot. storage = early studies demonstrated quantal nature of tranmission (hinted at existence of ‘packages’)
developents in microscopy lead to packagess being ideatified as vesicles
cryoelectron microscopy identified protein rquired to dock vesicles at membrane = SNARE proteins
new reaserch investigates molecular mechanisms for regulating release: vesicles involved in exocytosis have calcium sensor proteins = synaptotagmin

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19
Q

Termination of action

A

transmission needs a process that will rapidly dispose of released neurot
cholinergic synapses - enzyme = acetylcholinesterase
other synapses rely on uptake back into neutron for supporting cells - specific transporters for diff types of neurotransmitters

20
Q

Pharmacology principles

A

1) drug action must be explicable in terms of conventional chemical intercations between drug and tissues
2) drug molecules must be ‘bound’ to particular constituents in order to prudce effect
3) drug molecules must exert some chemical influence on one or more constituents of cells to produce a pharmalogical response

21
Q

Drugs interfere with neurotransmission, used to allevaite neurological conditions

A

antidepressants - can target transporters, block protein site so neurot isnt disposed of
amphetamines - indirectly increase noradrenaline release ny displacing it from its vesicles
ion channels - e.g. lignocaine, gabapentin
receptors - e.g. opium

22
Q

Receptors (pharm definition)

A

protein that binds chemical mediators e.g. hormones, neurot

23
Q

functions of receptors

A

regulation of cellular processes
1 - chemical recognition and binding
2 - intracellular signal generation

24
Q

Classified by structure

A

4 main classes
‘super families’
same class = common overall structural features
3 classes found on cell surface

25
Q

STRUCTURE 1) Ligand gated ion channel (ionotropic receptors)

A

control flow of specific ions across membrane, binding site facing outside, in series with a number of trans membrane domains

26
Q

STRUCTURE 2) G protein coupled receptor (metabotropic receptors)

A

all proteins that code for these have 7 transmembrane domains, anchors them into membrane
depending on sub family - binding domains in either amino terminus or ligand binding domain maybe in a ‘pocket’ inside membrane, have conservation in intracellular loops
recognised by and bind G proteins

27
Q

STRUCTURE 3) kinase - linked receptors

A

simple, single trans membrane domain, ligand binding site in amino terminus, range of bidning sites, used in immune and hormone signalling, transduction done by kinase being associated with them (phosphorylates other proteins)

28
Q

STRUCTURE 4) Nuclear receptors

A

no transmem domains, common drug target, found in cytoplasm or nucleus have DNA binding sites built in, directly control transcription of specific genes, used by lipophilic mediators

29
Q

agonist

A

bind to receptor to produce a response e.g. pilocarpine, nicotine, acetylcholine

30
Q

antagonist

A

prevent/inhibit response of an agonist e.g. atropine, curare, naloxone

31
Q

ligand

A

any molecule that binds to receptor

32
Q

signal transduction in:

ligand gated ion channel

A

most rapid
proteins arrange to open pore and ions flow through
milliseconds
e.g. nicotinic ACh receptor

33
Q

signal transduction in:

G protein coupled receptor

A

agonist bound receptor, activates G protein whic controls function of other proteins - could be enzymes or ion channels in membrane
seconds
e.g. muscarinic ACh receptor

34
Q

signal transduction in:

kinase linked receptor

A

increased / decreased expression of certain genes
hours
e.g. cytokine receptors

35
Q

signal transduction in:

nuclear receptors

A

regulate transcription
hours
e.g. oestrogen receptor

36
Q

Ligand gated ion channels

A

fast transmission
endogenous (ones we produce ourselves) agonists are fast / classic neurotransmitters, stored in synaptic vesicles e.g. ACh, glutamate, GABA
3-5 subunits
each subunit has 2 - 4 transmembrane domains
complex arrangemnt to form central aqueous pore
agonist binding = channel opening - channel is closed when agonist removed or receptor enters ‘desensitised’ state
ions flowing through open channels produce changes in cell potential e.g
excitatory neurotransmitter = ACh in PNS, glutamate in CNS = mem depolarisation, action potential firing
inhibitory neurot = inhibit mem depol, reduce action potenital firing

37
Q

sub families of ligand gated ion channels

A

1) cys-loop (pentameric assembly) e.g. nAChR, GABAR
2) ionotropic glutamate (tetrameric assembly), contain p loop e.g. NMDA
3) P2X (trimeric assembly), contain ATP gated channels, e.g. P2XR
4) calcium release (tetrameric assembly), e.g. IP3R

38
Q

Nicotinic receptor subtypes (3)

A

muscle type
ganglion type
CNS type

39
Q

Muscle type nicotinic receptors

  • location
  • membrane response
  • agonist
  • antagonist
A
  • skeletal NMJ post synapse
  • excitatory EPP
  • ACh, CCh
  • alpha-bungarotoxin , tubocurarine
40
Q

Ganglion type nicotinic receptor

  • location
  • membrane response
  • agonist
  • antagonist
A
  • autonomic ganglia, post synapse
  • excitatory, EPSP
  • ACh, CCh
  • trimetaphan
41
Q

CNS type nicotinic receptor

  • location
  • membrane response
  • agonist
  • antagonist
A
  • brain, pre and post
  • mainly pre-synaptic
  • ACh, DMPP
  • mecanylamine
42
Q

G protein coupled receptors (metabotropic)

A

receptor formed from single protein
7 transmem domains, heptohelico
heterotrimeric - 3 diff proteins form a G protein
regulate effector proteins
following agonist binding to a GPCR = signal transduction occurs via activation of heterotrimeric G proteins
activated subunit binds guancine triphosphate ( G receptor)
20 types of G protein, diff receptor sub types signal via diff G proteins
same G protein may be used by more than one receptor
3 subunit = alpha, beta, gamma, allow receptor to talk to and regulate effectors
act as switches

43
Q

GPCR ‘on’

A

signal molecule activates receptor
alpha contains binding site for nucleotide, forms complex with beta,gamma
agonist bound receptor is in direct contact with alpha subunit using intracellular loops for interaction
receptor binding causes change in alpha subunit = GDP affinity lowers, GTP affinity increases
receptor comes off alpha so alpha separates from beta,gamma

44
Q

GPCR ‘off’

A

alpha is bound to GTP
target protein is activated and GTP hydrolysed
alpha subunit now inactive - dissociates from target and reassembles with beta,gamma to reform inactive G protein
G proteinmay extend signal after signal molecule has gone

45
Q

Subunits :

alpha (a)

A

knwon for regulating activity if enzymes involved in producing 2nd messengers
e.g. Gs (a) = stimulates, inc adenyl cyclase = inc cAMP
Gi (a) = inhibits, dec adenyl cyclase = dec cAMP
Gq (a) = activate, inc phospholipase C (PLC) = inc IP3 + DAG = inc Ca in cell

46
Q

Subunits:

beta,gamma (bg)

A

known for regulating ion channels, reduced action potential firing
e.g. GIRK = potassium channel opened by bg subunit
opiod receptors act via G proteins, inc GIRK and dec Ca = dec pain transmission in CNS
dec cAMP = addiction

47
Q

Adenyl cyclase

A

2nd messenger for cAMP, regulates activity of other proteins in sig trans including PKA, EPAC and GREB
PKA = kinase that phosphorylates other proteins, made of regulatory and catalytic subunits, cAMP binds to regulatory subunits so they fall off to free up catalytic subunits to interact with downstream targets
e.g. in cardiac muscle beta 1 receptors are activated by adrenaline = inc cAMP = inc PKA = phosphorylates Ca channel = inc contractility
e.g. PLC activation by GPCRsleads to generation of 2nd messenger IP3 (which diffuses from membrane and releases Ca from ER) and DAG (which stays in plasma membrane and activates protein kinase c)
e.g. smooth muscle contraction stimulated by receptors coupled to Gq and PLC signalling = inc Ca = contraction

Physiology and Pharmacology (17 decks)

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