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Flashcards in Neurotransmitters Deck (75):
1

What 4 criteria does a neurotransmitter need to satisfy?

1. Synthesis: the NT must be made in the pre-synaptic neuron

2. Storage: the NT must be stored pre-synaptically in vesicles (exception is NO)

3. Release: NT must be released on demand

4. Inactivation: NT must be inactivated

2

What can happen to the NT after it binds and activates post-synaptic receptors?

+ Enzyme activation
+ Diffusion
+ Re-uptake

3

What is a receptor?

A protein that is either in the plasma or inserted in the outer membrane of a cell

4

What is the relationship between the receptor and a NT?

+ The receptor binds to and is activated by a NT

+ Lock and key hypothesis

+ Most receptors types are activated by only one NT but there are families of receptors sensitive to a single NT. exceptions include co-agonists, constitutively active receptors

5

What are the neurotransmitter classifications by structure?

+ Amino acids (simple compound with carboxyl group and amino group)

+ Biogenic amines:
- catecholamines
- indolamines

+ Peptides


6

What are the different amino acid neurotransmitters?

+ Glutamate
- primary excitatory NT of CNS
- acts through calcium ions

+ GABA
- inhibitory
- aminobutyric acid

+ Glycine
- inhibitory

(Other AAs: Aspartate, proline, taurine, beta-alanine)

7

What are the different biogenic amine neurotransmitters (catecholamines)?

+ Norepinephrine
+ Epinephrine
+ Dopamine

8

What are the different biogenic amine neurotransmitters (indolamines)?

+ Serotonin

9

What are the different peptide neurotransmitters?

+ Encephalin
+ Endorphin
+ Dynorphin

(Others include: Substance P, neuropeptide Y, neurotensin, cholecystokinin)

10

Where are the amino acid neurotransmitters produced?

In the bouton

11

What are functions of NT glutamate?

+ Action at post synapse predominantly by opening cation (e.g Na+) channels

+ Inactivation is by re-uptake and is recycled to either glutamate or GABA

12

What is the term for neurons within or spanning hemispheres?

Intra and inter-hemispheric connections

13

What are the terms for neurons descending to the braintstem or spinal cord?

+ Corticobulbar tracts

+ Corticospinal tracts

14

What other receptors are also permeable to calcium ions?

+ AMPA
+ Kainate
+ NMDA

15

What type of transmission are kainate glutamate receptors involved in?

Fast synaptic transmission and synaptic plasticity

16

What type of transmission are NMDA receptors involved in?

Slow synaptic transmission

17

Which neurotransmitter is involved in memory, learning and cell death?

Glutamate

18

What is synaptic plasticity?

+ The process by which synapses are strengthened or weakened by feedback mechanisms

+ Basic process for storing long and short term memories

19

What is the result of excessive glutamatergic stimulation of NMDA receptors?

A large influx of calcium ions; through a variety of processes this can result in cell death known as EXCITOXICITY

20

Which neurotransmitters is involved in migraines?

Glutamate

21

What can happen in regards to excess excitation?

It can feedback on itself to cause uncontrolled waves of excitation over expanding areas in the brain

22

What do the results of excess excitation manifest as at first?

+ Begin as PARTIAL COMPLEX seizures (partial - not the whole brain, complex - due to an alteration of consciousness)

23

What can the partial complex seizures progress to, and what causes the progression?

Grand Mal seizures (involve the whole brain):
- if the waves of depolarisation become more uncontrolled

24

How are seizures treated, and what do the treatments do?

With BENZODIAZEPINES:

- increase the action of GABA and drugs like PHENYTOIN which increase inactivation (refractory) period between firings in voltage activated Na+ channels

25

Why do benzodiazepines increase the action of GABA?

+ They act on a separate receptor binding site on the GABAa receptor, compared to GABA

+ This binding site controls the ability of GABA to open the channel; more benzodiazepines bound => GABA can open the channel more often

+ Benzodiazepines therefore only enhance the action of existing GABA molecules

26

What are some features of GABA?

+ Principle inhibitory NT of the CNS

+ Made from glutamate

27

Where is GABA found?

+ Predominantly in the interneurons of the CNS

+ Neurons of the striatum and globus pallidus, where it modulates descending motor information

28

GABA acts at ligand gated chloride channels (not K+ channels). What is it inactivated by?

Pre-synaptic reuptake

29

Name disease resulting from GABAergic dysfunction

Huntington's

30

What is the role of GABA in Huntington's, and what is the treatment?

+ GABAergic neurons degenerate, which can lead to uncontrolled movement

+ Treatment: GABA mimetic

31

What are the effects of alcoholism on GABA, and what are the treatments?

+ Causes a change in GABA transmission such that withdrawal results in convulsive movements and seizures

+ Treatment: Benzodiazepines (Diazepam, temazepam) and phenytoin

32

For what are GABA agonies sometimes used?

+ Treatment of anxiety
+ Treatment of sleeplessness
+ Treatment of epilepsy
+ Anaesthetics (e.g propofol)

33

What are some features of glycine?

+ Second most common inhibitory NT of the CNS

+ Synthesised from serine

+ Predominant inhibitory NT in the interneurons of the spinal cord and brain stem but also present in the brain

34

What is glycinergic dysfunction thought to be the cause of?

Inherited mammalian myoclonus
- most are benign
- others are late symptoms of more serious diseases

35

What causes tetanus, and how does it do so?

+ Caused by a toxin from the bacteria clostridium tetani

+ It inhibits the release of glycine resulting in a shift of the excitation-inhibition balance

36

What are the mild and serious effects of tetanus/shifts in excitation-inhibition balance?

Mild effects:
- restricted to muscles in Webster by cranial nerves

Serious effects:
- loss of inhibition in the cerebra => epiform fits

37

What is the treatment for tetanus/shifts in the excitation-inhibition balance?

Injection of antitoxin which binds the toxin and benzodiazepines which boost GABAergic pathways

38

What are some features/functions of norepinephrine?

+ Aka noradrenaline

+ Sympathetic NT: inhibition

+ Used in treatment for:
- Parkinson's
- ADHD

+ Agonsists:
- cocaine
- tricyclic antidepressants

+ Projects major centres of the brain

39

What are some features/functions of epinephrine?

+ Aka adrenaline
+ Peripheral hormone from adrenal medulla
+ Pharmacological target for cardiac and circulatory problems

40

What are some features/functions of dopamine?

+ NT and neuromodulator
+ Involved in pleasure, addiction and movement
+ Dopaminergic axons project to the majority of the CNS (excluding cerebellum)
+ Act at G-protein linked metabotropic receptors

41

Where are catecholamine NTs synthesised?

+ In the bouton

+ Inactivated principally by re-uptake

42

What are adrenoceptors?

G-protein linked metabotropic receptors

43

What NTs are involved in the fight or flight response (gut, heart, respiration etc)?

Epinephrine and norepinephrine

44

What does the brainstem in the CNS use norepinephrine to influence?

+ Sleep
+ Wakefulness
+ Attention (via reticulum)
+ Feeding behaviour (via hypothalamus)
+ Involved in bi-polar disorder

45

What is the Locus Coeruleus?

The part of the brainstorm whose neurons project norepinephrinergic axons

46

How many different central systems is dopamine found in and what is it involved in?

+ 3 different central systems

1. The control of movement

2. Certain symptoms of psychiatric disease

3. Regulation of the release of certain hormones

47

Control of hormone release is exerted by dopamine. Where does this occur, and what is the role of dopamine?

+ Anterior pituitary

+ Dopamine released into portal vessels by hypothalamic neurons

48

What is the role of dopamine in Parkinson's?

Parkinson's sufferers who experience tremors, muscle rigidity and bradykinesia or akinesia have DEPLETED dopamine in the MOTOR CO-ORDINATION CIRCUITS

49

What is the role of dopamine in schizophrenia?

+ Can be caused by an OVER PRODUCTION of dopamine in the Mesolithic system

+ Treatment with antipsychotics

50

How is dopamine related to addiction of drugs of abuse, decide, and certain behaviours such as sexual activity?

Dopamine works through the pleasure centres of the CNS located in the mesolimbic dopamine system

51

What are some features/functions of serotonin?

+ Neorons originate principally in Raphe nuclei in the brainstem

+ Project to the majority of the brain and brainstem

+ Large family of both excitatory and inhibitory receptors, in the CNS & PNS

+ Modulates a range of NTs such as glutamate, GABA and dopamine

+ Functions associated with sleep, anxiety, depression and mood swings

52

What is serotonin dysfunction (reduction) associated with, and how can it be treated?

+ Associated with depression and obsessive compulsive disorder (OCD)

+ Treatment: fluoxetine (Prozac a 5-HT re-uptake inhibitor)

53

What are the receptor agonists involved in the serotonergic systems (often exploited by drug users) and what do they do?

+ LSD
+ Psilocybin
+ Mescaline

Inhibiting mono amine catabolism generally with MAOIs (monoamine oxidative inhibitors)

OR

Inhibiting serotonin re-uptake

=> increases 5-HT levels

54

What are examples of psychostimulants?

+ Amphetamines
+ Ecstasy

55

What are features of amphetamines?

+ Cause release of amines such as NA, 5-HT and dopamine
+ Also inhibit re-uptake of NA, 5-HT and dopamine thus causing enhanced activation of these receptors

56

What are features of ecstasy?

+ Amphetamine analogue: methylenedioxymethamphetamine or MDMA

+ Has numerous actions but its major effect is by causing the release of and preventing re-uptake of 5-HT

57

Which peptide NT is involved in Pain transmission

Substance P

58

Which peptide NTs are all implicated in schizophrenia?

+ Neuropeptide Y
+ Neurotensin
+ Cholecystokinin

59

Which NTs are associated with the perception of pain?

Endorphins and encephalins

60

What are the features/functions of endorphins and encephalins?

+ They act as opitate receptors in the brain and spinal cord where they are the endogenous ligand

61

What are some examples of opiates?

+ Morphine
+ Codeine
+ Pethidine
+ Methadone
+ Diamorphine (heroin)

62

What does taking opiates lead to?

+ Down regulation of opiate receptors throughout the CNS

+ This causes opioid tolerance and increased intake

63

What is the result of there being opioid receptors in the limbic system (and the periaqueductal grey)?

+ Opiates affect emotional perception as well as pain

+ Emotional element to withdrawal avoidance

64

To whom is naxalone given, and what is its purpose?

It is given to withdrawing heroin addicts to reduce symptoms

65

What is naxalone?

An opiate receptor agonist

66

Give an example of an ester NT?

Acetylcholine (ACh)
+ An unusual NT but first one discovered
+ Used as a standard setter for defining NTs

67

What are features/functions of the NT- acetylcholine?

+ Principle excitatory NT
+ Found in both CNS and PNS

68

Where do the neurons of ACh project to?

The hippocampus & the cortex: essential for the formation of new memories and learning

69

What is associated with ACh dysfunction (reduction)?

Alzheimer's disease

70

Which drugs act on AChs receptors?

+ Nicotine (drug of abuse)
+ Muscarine (agonist)
+ Atropine (antagonist)
+ Tropicamide (antagonist to dilate pupils during surgery)

71

What do anticholinesterases prevent?

The breakdown of ACh

72

What are some examples of anticholinesterases?

+ Insecticides (DDT)
+ Nerve gasses (Sarin)

Alzheimer's treatments: Donepezil (aricept)

73

What is Korsakoff's psychosis?

The diet of an alcoholic often leads to a thiamine deficiency causing famage to the thalamus and the mammillary bodies

74

What are the syptoms of Korsakoff's psychosis?

+ Amnesia
+ Confabulation
+ Lack of insight
+ Apathy

75

Are there treatment options for Korsakoff's psychosis?

The cells involved are cholinergic and partial recovery can sometimes be achieved by using anticholinesterases