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Physiology and Pharmacology of Cells > L5 - Drug Action in the CNS - Anxiolytics > Flashcards

L5 - Drug Action in the CNS - Anxiolytics Flashcards

1
Q

What are the 5 types of anxiety?

A 
Generalised anxiety 
Panic disorder
Phobias
Posttraumatic stress disorder
Obsessive compulsive disorder
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2
Q

What is generalised anxiety?

A

No clear reason or focus

Symptoms interfere with normal behaviour

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3
Q

What is panic disorder?

A

Overwhelming fear to a particular situation

Marked somatic symptoms – activation of sympathetic nervous system

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4
Q

What is PTSD?

A

Fear associated with a memory

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5
Q

What is OCD?

A

Reproductive behaviour - not normally a productive behaviour
Physical demonstration of a stress response

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6
Q

What are benzodiazepines?

A 
Anxiolytics 
E.g. diazepam 
Have a quick calming/sedative effect 
Often used to treat panic disorders 
Long term use has some negatives 
- Addictive 
- Tolerance develops 
- Sedative
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7
Q

What are anti-depressants?

A

E.g. SSRIs
If you can manage the depression the management of the anxiety comes within
Take several weeks to become effective
- Often prescribe benzodiazepines while you are waiting

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8
Q

What are buspirones?

A

5HTIA agonist
Takes several weeks to become effective
Shows its anti-anxiety effects without any negative side effects
Has no hypnotic activity – does not make you drowsy

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9
Q

What are beta blockers?

A

E.g. propranolol

Blocks sympathetic physical displays of anxiety

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10
Q

What are animal models of anxiety based on?

A

Based on fear or conflict within the animals

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11
Q

What is the elevated cross animal model?

A

At one side of the cross you have walls, on the other side you don’t
Rodent tends to go on the side of the cross that has the walls
- Has less fear of falling off
If rodent treated with anxiolytics it spent equal time on each side of the cross

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12
Q

What is the light/dark box animal model?

A

Rodent tends to go on the dark side of the box

If rodent treated with anxiolytics they will spend equal time on each side of the box

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13
Q

What did animal models of anxiety show?

A

Studies using these behavioural tests which rely on rodents innate fear responses showed GABA plays a major role

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14
Q

What are some examples of excitatory amino acids?

A

Glutamate

Aspartate

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15
Q

What are some examples of inhibitory amino acids?

A

GABA

Glycine

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16
Q

GABAa receptor overview

A 
GABAb receptors not affected in anxiety 
Ionotropic receptors - ligand gated 
Chloride Selective
Nicotinic 
5 subunits - 2α : 2β : 1γ
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17
Q

What do GABAa receptors mediate?

A

Mediate fast inhibitory transmission between neurons – postsynaptic
Can hyperpolarise neuron to stop it reaching threshold
Can cause input resistance to hyperpolarise neuron

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18
Q

What are the agonists at the orthosteric sit of GABAa receptors?

A

Muscimol

  • Used to distinguish between GABAA and GABAB
  • When agonist binds the channel opens
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19
Q

What are the antagonists at the orthosteric sit of GABAa receptors?

A

Bicuculline

Picrotoxin

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20
Q

What are the inverse agonists at the orthosteric sit of GABAa receptors?

A

Beta-Carboline

- Decreases the responsiveness of the receptor to its natural agonist

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21
Q

What are the agonists at the allosteric sit of GABAa receptors?

A

Diazepam

22
Q

What are the antagonists at the allosteric sit of GABAa receptors?

A

Flumazenil

- Useful for the treatment of an overdose

23
Q

What are GABAa receptors regulated by?

A

Barbiturates – used in euthanasia
Neurosteriods
General anaesthetics

24
Q

What GABAa receptors targets for?

A 
Sedatives 
Anxiolytics
Hypnotics
Anti-convulsants
General anaesthetics
25
Q

What is the effect of alcohol at the GABAa receptor?

A

Mixing benzodiazepines and alcohol has negative impact

26
Q

How can you model animal aggressive behaviour?

A

Aggressive behaviour induced by isolation followed by introduction of new animal

27
Q

What amino acid change leads to reduction in the affinity of benzodiazepines?

A

His→Arg mutation

28
Q

When was knock in experiments used in mice?

A

Creation of mice containing His→Arg mutation in α subunit

  • Show a loss in affinity for benzodiazepines at GABAA receptors containing mutated subunit
  • When in light/dark box no longer showed a preference
  • No other effect on the receptor
29
Q

What are the physiological effects of Benzodiazepine agonist?

A 
Sedation/anxiolytic 
Hypnosis 
Anterograde amnesia 
Anti-convulsant 
Reduction of muscle tone
30
Q

What is sedation/anxiolytic?

A

Decreased responsiveness to constant level of stimulation

31
Q

What is hypnosis?

A

Latency of sleep onset is decreased
Duration non-rem sleep increased
Duration of rem sleep decreased
Duration of slow-wave (associated with sleep walking and night terrors) sleep decreased

32
Q

What is anterograde amnesia?

A

Prevents memory of events experienced while under the influence of the drug
o Eg. Flunitrazepam – date rape drug

33
Q

What is anti-convulsant?

A

Inhibit development and spread of epileptiform activity

34
Q

What is the reduction in muscle tone?

A

Due to effects of GABA transmission in the CNS

35
Q

What are the possible ways benzodiazepines can increase the activity of GABAa receptors?

A

Increases Cl current
Increases frequency of channel openings
Increases channel open time and decreases channel close time
Increases channel conductance

36
Q

How did they work out which method benzodiazepines used to increase the activity of GABAa receptors?

A

Carried out single channel studies and patch clamping with and without Benzodiazepines

37
Q

What is the difference between the modulation of GABAa receptors by Benzodiazepines vs. Barbiturates?

A

Benzodiazepines increase probability/frequency of opening
- Increase the affinity of the receptor for GABA
Barbiturate and steroids increase mean open time
Both result in more current flow and bigger response

38
Q

What is beta carboline?

A

Inverse agonist

In the presence of GABA – cause the channel to open less

39
Q

What is Flumazenil?

A

Competitive antagonist
Prevents or reverses the action of an agonist
Useful for treatment of overdoses of benzodiazepines

40
Q

What pharmacokinetic properties of Benzodiazepines determine their therapeutic use?

A 
Lipid solubility 
Redistribution and accumulation 
Onset of action
Drug half life 
Presence of active metabolites 
Plasma protein binding
41
Q

What is drug half life dependent on?

A

Dependent on renal function – age and microsomal enzyme induction

42
Q

Diazepam metabolism

A

Metabolized to produce active intermediates with very long-half life – prolongs its activity
Intravenous diazepam - treat status epilepticus
Long 1-2 days duration of action

43
Q

Zolpidem metabolism

A

Short 2-hour half life

Short 4-hour duration of action

44
Q

What are the adverse effects of Benzodiazepine Agonists

A 
Sleepiness, impaired psychomotor function, amnesia
Additive effects
Tolerance
Misuse
Physical dependence
45
Q

Why are Benzodiazepines not useful for generalised anxiety?

A

Not useful for long term issues due to sleepiness effects

46
Q

What are the different types of tolerance of Benzodiazepines?

A

Decreased responsiveness to a drug following continuous exposure
May be overcome by increasing dose
Changed responsiveness of CNS - with benzodiazepines
Metabolic tolerance - with barbiturates

47
Q

Physical dependence of Benzodiazepines

A

Characterized by withdrawal
Increased anxiety, insomnia, CNS excitability, convulsions
More problematic with drugs with short half lives - E.g. triazolam may cause daytime anxiety
Withdrawal may be alleviated by using slower acting drug

48
Q

At what stage does benzodiazepine decrease its effects?

A

Decreases its effects at the level of hypnosis

Only increases activity of GABA in area of brain where is ongoing GABA activity

49
Q

At what stage do barbiturate decrease their effects?

A

Does not decrease its level of activity and can lead to anaesthesia and comas
May be rescued by addition of Flumazenil

50
Q

What are some examples of other anxiolytics and hypnotics?

A

Benzodiazepine partial agonists
- Will lead to less tolerance and physical dependence
Receptor selective benzodiazepine agonists
Non-benzodiazepines
- Buspirone 5HT 1 agonist - non-sedative
β-Adrenoceptor antagonists
- Propranolol
- Used to block physical symptoms associated with activation of sympathetic nervous system
Over the counter sleep aids – anti-histamines
- Promethazine

Physiology and Pharmacology of Cells (13 decks)

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