Monoamines Flashcards
What are the CNS systems that control behaviour?
→ Autonomic nervous system
→ Hypothalamic-pituitary neurohormones
→ Diffuse monoamine systems
What are examples of monoamines?
→ Noradrenaline
→ Serotonin
→ Dopamine
→ ACh
What neurons project from the central core?
→ Adrenergic
→ Serotonergic
→ Dopaminergic
→ Cholinergic
What are the four systems with common principles?
→ Small set of neurons at the core
→ Arise from the brain stem
→ One neuron influences many others
→ Synapses release transmitter molecules into extracellular fluid
What is the main source of noradrenergic neurons in the brain?
→ Locus Coeruleus
What is the main source of serotonergic neurons in the brain?
→ Raphe Nuclei
What are the main sources for the dopaminergic neurons in the brain?
→ Substantia nigra
→ Ventral tegmental area
What are the main sources for cholinergic neurons in the brain?
→ Basal forebrain and brain stem complexes
What 3 things are involved in fast point-to-point signalling? (type of channel and transmitter)
→ Neurotransmitters producing excitatory or inhibitory potentials
→ Ligand gated ion channels
→ Glutamate, GABA, ACh
What 3 things are involved in slow transmission?
→ Neurotransmitters and neuromodulators
→ G-Protein coupled receptors
→ Monoamines, peptides, ACh
Where do noradrenergic neurons project from?
→ Central core
What 5 areas of the brain do noradrenergic neurons project to?
→ Cortex
→ Amygdala
→ Hypothalamus
→ Spinal cord
→ Cerebellum
What is the locus coerulus involved in?
Making the brain more responsive
→ Information processing
What is noradrenaline involved with?
→ Gambling
What are withdrawal symptoms driven by?
→ Hyperexcitability from noradrenaline
What receptors does noradrenaline act on?
→ G coupled post-synaptic receptors
→ activates presynaptic alpha 2 receptors
What are noradrenergic alpha 2 receptors also called and why?
→autoreceptors
→ When noradrenaline binds it inhibits the release of noradrenaline
What do low levels of noradrenaline lead to?
→ Depression like behaviour
How is the action of noradrenaline terminated?
→ Inside the membrane there are NET transporters
→ Uptake excess noradrenaline inside the neuron
→ Once inside they get broken down by monoamine oxidase
How do amphetamines work?
→ They enter vesicles and displace the NA into the cytoplasm which causes NA leakage out of the neuron
What does cocaine do?
→ Blocks NA reuptake
What is the main action of noradrenaline receptors?
→ Inhibitory ( alpha 2)
→ Also excitatory (alpha/beta)
How is noradrenaline terminated?
→ Neuronal uptake
→ MAO
What is the main cell body of noradrenaline?
→ Locus coerulus
When are noradrenergic neurons active?
→ When awake
Where are high densities of noradrenergic neurons found?
→ Brainstem
→ Hypothalamus
→ Medial temporal lobe
What are the functions of noradrenergic neurons?
→ Arousal
→wakefulness
→ mood
→ Blood pressure regulation
Describe the nigrostriatal pathway?
→ Dopaminergic neurons project from the substantia nigra to the striatum
Why does Parkinsons occur?
→ Dopaminergic neurons become degenerated
Describe the mesolimbic pathway?
→ Dopaminergic neurons project from the ventral TA to
→ amygdala
→ Hippocampus
→ Nucleus Accumbens
What is the function of the nucleus Accumbens?
→ Rewards and pleasure
What is schizophrenic behaviour due to?
→ Hyperactivity of the mesolimbic pathway
Describe the mesocortical pathway?
→ Dopaminergic neurons projecting from the VTA to the cortex
Describe the tuberohypophyseal pathway?
→ Dopamine is released from the hypothalamus directly to the circulation
In what situation does dopamine act as a neurohormone?
→ It goes to the anterior pituitary and inhibits the release of prolactin
What receptors are activated during emesis?
→ D2 receptors
Describe the formation of dopamine
→Tyrosine gets metabolised by tyrosine hydroxylase
→ this forms DOPA
→ DOPA gets metabolised by DOPA decarboxylase to form dopamine