HMB200H1 Lecture Notes - Tryptophan, Cholinergic, Tyrosine

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Lecture 4 - Transmitters and Secondary Messenger
-Transmitters are usually amines(derived from single A.A tryptophan or tyrosine).
Others can be other A.As, like Glutamate and Glycine, and some can be derived
from converting the amino acids, like GABA which is made from Glutamate by
Glutamic Acid Decarboxylase (GAD)
- Glutamate: is an amino acid that can act as transmitter. It is the most important
excitatory trasnmitter. (exclusively)
- Glycine and GABA is the most important inhibitory transmitter. (exclusively)
- GABA is the most common inhibitatory transmitter in the forebrain. Its made from
glutamate by the enzyme GAD. (excitatory -> inhibitatory) The presence of GAD
can thus be used to find inhibitatory neurons.
- If you have GAD, the glutamate will always be converted to GABA, so it
CANT be excitatory. Meaning there is a seperation between exc. glutamate
neurons and inhi. GAD positive GABA neurons.
- Other transmitters like ACh and Serotonin can be both inh. and exc. depending on
the receptors. They act on different types of receptorts and thus either have
depol.ing exc. effect or hyperpol.ing inhibitatory effect.
- These are found in small number of neurons inside the brain since the most
common ones are GABA and Glutamate.
- Transmitters that have mixed effects are found in identified cell groups throughout
the brain:
-ACh: 1% - 2% of the neurons in the brain have ACh. All of the motor neurons are
ACh.
- in the spinal cord, ACh is the exc. transmitter to muscles, and in the
brainstem, the exc. motor neurons that go to muscles of
the face and neck also use ACh.
- Cholinergic Cell Groups Ch 1 - 6
- Cetecholamines are derived from the amino acid tyrosine.
- Tyrosine -> (tyorisine hydroxidase) L DOPA -> Dopamine -> Norepi ->
Epinephrine.
- you can tell which cetacholamine is present by looking at which enzyme is
present. All the neurons that use catecholamines must have tyrosine hydroxidase
to start to conversion.
- Catecholamines are found in cell groups A1-A17 in brain.
- Norepi: A1- A7 = in the brainstem.
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Document Summary

Transmitters are usually amines(derived from single a. a tryptophan or tyrosine). Others can be other a. as, like glutamate and glycine, and some can be derived from converting the amino acids, like gaba which is made from glutamate by. Glutamate: is an amino acid that can act as transmitter. It is the most important excitatory trasnmitter. (exclusively) Glycine and gaba is the most important inhibitory transmitter. (exclusively) Gaba is the most common inhibitatory transmitter in the forebrain. Its made from glutamate by the enzyme gad. (excitatory -> inhibitatory) the presence of gad can thus be used to find inhibitatory neurons. If you have gad, the glutamate will always be converted to gaba, so it excitatory. Meaning there is a seperation between exc. glutamate. Other transmitters like ach and serotonin can be both inh. and exc. depending on the receptors. They act on different types of receptorts and thus either have depol. ing exc. effect or hyperpol. ing inhibitatory effect.

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