7.6 Neuromodulatory Transmitter Systems

Question 1

What is a neuromodulator?

Answer 1

Substance of transmitters which modulate the efficacy of synaptic transmission but cannot produce firing alone
Mainly act via metabotropic receptors

Question 2

What are the catecholamines?

Answer 2

Dopamine and noradrenaline

Question 3

What is the biosynthesis of catceholamines?

Answer 3

Tyrosine (tyrosine decarboxylase) - L-DOPA (amino acid decarboxylase) - Dopamine (dopamine B hydroxylase) - Noradrenaline (phenylethanolamine-N-methyltransferase) Adrenaline

Question 4

Which molecule in the biosynthesis of catecholamines can cross the BBB?

Answer 4

L-DOPA

Question 5

What breaks down catecholamines?

Answer 5

MAO and COMT

Question 6

Where are the dopamine nuclei found and where do thy project to? and which diseases are implicated in each?

Answer 6

Substantia nigra - project to the striatum of the basal ganglia and facilitate the initiation of movement - PARKINSONS

Ventral tegmental area: innervate the forebrain which includes the pre-frontal cx and parts of the limbic system - SCHIZOPHRENIA

Question 7

Where does the noradrenergic system start and project to?

Answer 7

Starts in the locus coeruleus and the reticular formation and projects to many parts of the cortex including the cerebellum, thalamus, neocortx, hypothalamus, amygdala and hippocampus

Question 8

What is the transduction and function of the NA system?

Answer 8

Transduction is via adrenergic receptors

Function: attention and vigilance and phasic changes in levels of attention

Question 9

What drug acts on the NA system?

Answer 9

Amphetamines

Question 10

What are the ionotropic and metabotropic receptors for serotonin?

Answer 10

Metabo: 5-HT 1,2 and 4-7
Iono: 5-HT3

Question 11

What does serotonin need to be made?

Answer 11

Vitamin B6

Question 12

Where are serotonin neurons located and where do they project to

Answer 12

Locates in the raphe nucleus (caudate and rostral) with very dense and profuse innervation

Question 13

What is the function of the serotonin system?

Answer 13

Sleep-wake cycle
Aggression and impulsivity
Anxiety and depression
Descending pain control

Question 14

What drugs exert their effects through the 5-HT system?

Answer 14

LSD

Question 15

What is the iono and metabotropic receptors for ACh?

Answer 15

Iono: pentamer of 2a, Ib, Igamma, 1 delta subunis
Metabo: M1-5

Question 16

Where are ACh neurons found and where do they project to?

Answer 16

Basal forebrain: nucleus basils and septal nuclei
- hippocampus and all neocortex
Pontomesencephalo-tegmental complex
- thalamus and part of forebrain

Question 17

What is the function of the cholinergic system?

Answer 17

Learning and memory - alzheimers

Arousal and sleep/wake cycle

Question 18

What drug acts on the cholinergic pathway?

Answer 18

Muscarine

Question 19

What is the receptor for orexin/hypocretin?

Answer 19

Metabotropic - OXIR1 and 2 which is coupled via Gq to IP3 pathway

Question 20

How is orexin/hypocretin broken down?

Answer 20

internalised as receptor/transmitter

Question 21

What is the function of the hypocretin/orexin system?

Answer 21

Master system
Provides wakefulness
At the interface between CNS and ANS - plays a role in metabolism and BP