0814 - Neuromodulatory Transmitter Systems

Question 1

What is a neuromodulator? How does it differ from a neurotransmitter?

Answer 1

A substance which alters the efficacy of synaptic transmission, changing the activity of the post-synaptic neuron to increase or decrease its firing rate.
It cannot produce firing if applied alone, and acts mostly via metabotropic receptors.

Question 2

List a variety of neuromodulators in the CNS

Answer 2

Catecholamines - Dopamine, noradrenaline
Serotonin (5HT)
ACh
Orexin and Hypocretin

Question 3

Outline the dopamine system

Answer 3

Dopaminergic cells in midbrain (co-released with Glu). Nuclei - Substantia nigra and ventral tegmentum.
Projects into basal ganglia and forebrain (cortex)

Question 4

Outline the noradrenergic system.

Answer 4

Predominantly in locus coeruleus (to cortex), also in reticular formation (to spinal cord).
Transduction via adrenergic receptors
Function - attention and vigilance

Question 5

Outline the serotonergic system

Answer 5

Concentrated in rostral and caudal raphe nuclei.
Extensive and profuse innervation - particularly sensory and limbic areas.
Function - Sleep/wake, aggression/impulse, anxiety/depression, descending pain control.

Question 6

Outline the cholinergic system

Answer 6

2 main areas - basal forebrain (nucleus basalis and septal nuclei) and pontomesencephalo-tegmental complex.
Modulates excitability
Function - Learning and memory, Arousal and sleep/wake.

Question 7

Outline the orexin/hypocretin system

Answer 7

Hypothalamic cell group.
Mostly excitatory. Acts as a ‘master’ system - promoting wakefulness, at interface between CNS and ANS (metabolism, BP etc).