neurotransmitatori 2 Flashcards
What are neurotransmitters?
Chemicals that allow the communication between a releasing neurone that sends signals across a synapse onto a target neurone, a gland cell or a muscle cell.
What is neurotransmitters function?
They play a major role in modulating several everyday functions.
What is the dopamine theory of schizophrenia?
Schizophrenia is caused by an overactive dopamine system in some regions of the brain, and underactive in other regions.
According to the dopamine theory, what leads to + symptoms?
Overactivity of the mesolimbic pathway
According to the dopamine theory, what leads to - symptoms?
Mesocortical pathway dysfunction
- What is evidence to support dopamine theory?
Drugs like cocaine and amphetamine which block the re-uptaking of dopamine produce sz-like behavioural effects.
- What is evidence to support dopamine theory?
Drugs that block dopamine receptors reduce sz symptoms and have side effects similar to Parkinson’s disease (caused by lack of dopamine in the basal ganglia)
- What is evidence to support dopamine theory?
Abnormal activation in prefrontal areas, basal ganglia and the striatum in people with sz.
What is evidence against the dopamine theory?
Dopamine is not the only NT involved in sz.
Antipsychotic medication may alleviate the positive symptoms of sz but do not significantly affect the negative symptoms, suggesting that there is more involved than abnormal dopamine levels alone.
What is the serotonin theory?
Recreational drugs like LSD or ecstasy produce behaviours and mental processes similar to sz.
These drugs act by blocking the effects of serotonin at specific receptors.
What is the glutamate hypothesis?
People with sz have a deficiency in a type of glutamate receptor known as NMDA.
Some recreational drugs cause sz-like symptoms by blocking NMDA glutamate receptors.
How does glutamate work in normal patients?
An important glutamatergic pathway originates in the ventral tegmental area (VTA).
This acts as a brake on the mesolimbic dopamine pathway by communicating with dopamine neurons in the VTA.
This results in inhibition of dopamine release from the mesolimbic pathway.
This prevents excessive dopamine release.
How does glutamate hypothesis work for positive symptoms?
Hypoactive NMDA receptors in the VTA cannot inhibit mesolimbic dopamine neurones.
This causes mesolimbic dopamine hyperactivity and the positive symptoms of psychosis.
How does the glutamate hypothesis work for negative symptoms?
Normally: Glutamate neurones synapse directly unto dopamine neurones in the VTA that project to the cortex.
These glutamate neurones function as accelerators of the mesocortical dopamine neurones and therefore excite them.
Sz: When NMDA receptors are hypoactive, they lose their excitatory drive. Therefore less dopamine is available in mesocortical neurones causing negative symptoms.
What can you say about glutamate hypothesis in your own words?
Normally in the mesolimbic system NMDA receptors are regulating so that there is not too much dopamine there.
But if NMDA receptors are not active then they cannot regulate the amount of dopamine and then there will be too much dopamine because the dopamine can’t be released from the mesolimbic pathway and too much dopamine is the cause of positive symptoms.
In the mesocortical system, glutamate neurones accelerate dopamine neurones. But if NMDA receptors are not functioning, then they can’t excite dopamine and levels drop causing negative symptoms.
