Neurotransmitters

Question 1

List the two inhibitory neurotransmitters in the nervous system.

Answer 1

1. GABA
2. Glycine

Question 2

List some (8) excitatory neurotransmitters found in the nervous system.

Answer 2

1. Acetylcholine (Ach)
2. Aspartate
3. Adrenaline
4. Dopamine
5. Histamine
6. Glutamate
7. Noradrenaline
8. Serotonin

Question 3

Glutamate is known as…

Answer 3

Amino acids that are always excitatory?

Question 4

What is the general main role of Dopamine?

Answer 4

Modifying somatic movements and happiness, emotion & behaviour are regulated by dopamine.

Question 5

What are the amino acid neurotransmitters in the nervous system?

Answer 5

Acetylcholine, Glutamate, Aspartate, GABA & Glycine are amino acid neurotransmitters.

Question 6

All of the drugs used in the stalling of progression of dementia (alztheimers disease) act on which type of neurotransmitters?

Answer 6

Amino acid neurotransmitters.
Of the 4 drugs 3 affect Acetylcholine pathways and the other effects Glutamate.

Question 7

What are the monoamine neurotransmitters (4) in the nervous system?

Answer 7

Adrenaline,
Noradrenaline,
Serotonin,
Dopamine.

Question 8

Are neuorpeptides such as substance p and endorphines considered neurotransmitter?

Answer 8

Yes

Question 9

What are the two nuclei and pathways effected in the cholinergic hypothesis of Alzheimers Disease?

Answer 9

Ach neuron nuclei implicated in Alzheimers Disease.
1. The Nucleus Basalis (nucleus > cortex).
2. The Septohippocampal nucleus (Septal area > via hypothalamus > hippocampus). (*key in learning and memory).
3. Pedunculopontine / lateraodorsal tegmental nucleus.

Question 10

What three drugs are used to treat Alzheimer’s Disease which act on Ach Pathways.

Answer 10

1. Donepezil
2. Rivastigmine
3. Galantamine

These drugs are AchE inhibitors that can cross the blood brain barrier thus they increase the amount of Ach in these neurons of the Basalis nucleus and the septohippocampal nucleus by preventing AchE from degrading the neurotransmitter Ach.

Question 11

There are four drugs used to treat Alzheimer’s Disease. Three are AchE inhibitors and the last is an NMDA antagonist. What is it called and how does it work?

Answer 11

Memantine is a NMDA (glutamate) receptor antagonist. Glutamate is a Amino Acid that is believed to be implicated in neuronal death in Alzheimer’s Disease thus it is theorised blocking Glutamate levels prevents neuronal cell loss.

Question 12

What is the MOA of botulinum toxin (Botox)?

Answer 12

Botox inhibits SNARE proteins from facilitating exocytosis of Ach from cholinergic neuron terminals. Because Botox has a very high affinity for cholinergic SNARE proteins. This prevents the normal SNARE protein facilitated exocytosis of Ach from cholinergic neurons thus causing a cholinergic deficit and therefore paralysis at the site of injection.

In the absence of ACH release from cholinergic neurons there is no Ach to bind to and stimulate skeletal muscle ligand gated channels, which would induce depolarisation > contraction of skeletal muscles.

Remember when Ca2+ enters the terminal button via the voltage gated ion chanel it is calcium that interacts with the SNARE proteins to promote transport of the vesicle to the synaptic cleft for fustion and exocytosis.

Question 13

Acetylcholine (Ach) works on which types of receptors?

Answer 13

1. Nicotinic (ligand gated ion channel)
   - NN (Ganglia)
   - NM (skeletal Muscle)
2. Muscarinic receptors (G protein coupled receptors)
   - M1 (Neuronal) -< Gq receptors
   - M2 (Cardiac tissue) -Gi receptors
   - M3 (Glandular tissue) -< Gq receptors

Question 14

What are common uses of Botox?

Answer 14

Wrinkle reduction,
Spacity

Question 15

What are the different types (3) of G protein coupled receptors?

Answer 15

1. Gs - stimulatory receptors
2. Gi - inhibitory receptors
3. Gq - super-stimulatory receptors

Question 16

Why does a cholinergic deficit lead to dryness of mouth?

Answer 16

Muscarinic receptors stimulated by Ach located on glands are Gq super-stimulator receptors). In the absence of / reduced levels of Ach salivary glands are not stimulated and therefore dryness of mouth is experienced.

Question 17

If Dopamine, Adrenaline and Noradrenaline are derived from the same precurser molecule, Tyrosine what makes Dopaminergic and Adrenergic neurons different?

Answer 17

Dopaminergic neurons contain only the enzymes:
TH (tyrosine hydroxolase / DDC / Aromatic AADC) which converts Tyrosine > Dopa; and
DOPA decarboxylase which converts DOPA > Dopamine.

Adrenergic neurons contain a further two enzymes:
Dopamine-B-hydroxolase to convert Dopamine > Noradrenaline; and
PENMT (phenylehanolamine-N=methyl transferase) to convert Noradrenaline > Adrenaline.

Question 18

What area of the brain has high amounts of adrenergic neurons?

Answer 18

Locus Coerulus

Question 19

What are the names of the main dopaminergic pathways in the CNS?

Answer 19

1. Nigrostriatal (smooth movement)
2. Mesolimbic (reward system)
3. Mesocortical (unknown role but inhibition causes ve- symptoms of psychosis)
4. Tuboinfundibular / tuberohypophyseal (connects hypothalmus to pituitary and increased stimulation reduces prolactin secretion).

Question 20

What does the Nigrostriatal pathway connect?

Answer 20

Substantia nigra (houses nuclei of dopaminergic neurons in this pathway) and connects to the > Striatum (caudate and putamen) to regulate out stop go signalling for smooth somatic muscle movements.

Question 21

What is another name for the reward pathway?

Answer 21

The mesolimbic pathway

Question 22

What does the mesolimbic pathway connect?

Answer 22

VTA (nucleus of the midbrain containing nuclei of dopaminergic neurons in the pathway) >
1. Amygdala
2. Nucleus Acumbens (striatum)
3. Limbic system

Question 23

What does the mesocortical pathway connect?

Answer 23

VTA (midbrain nuclei containing dopaminergic neurons) to the prefrontal cortical areas. The role is unknow however inhibition of this pathway leads to ve- symptoms of psychosis such as depression, reduced motivation, reduced skeletal muscle movement.

Question 24

What does the tuberoinfundibular / tuberohypophyseal pathway connect?

Answer 24

The hypothalamus to the pituitary gland (dopaminergic pathway) which when stimulated is involved in reducting prolactin secretion.