Class Notes (836,414)
Canada (509,777)
Psychology (4,066)
PSY2116 (56)
Lecture 8

lecture 8.docx

3 Pages
Unlock Document

Andre Lecours

Neurotransmitter Chemistry  Most of the known neurotransmitter molecules are either: o Amino acids o Amines derived from amino acids o Peptides constructed from amino acids  ACh is an exception; but it is derived from acetyl CoA,  Choline which is important for fat metabolism throughout the body  Amino acid and amine transmitters are generally each stored in and released by separate sets of neurons  Dale’s principle- idea that a neuron has only one neurotransmitter  Many peptide containing neurons violate Dale’s principle because these cells usually release more than one neurotransmitter: an amino acid or amine and a peptide  Co-transmitters- two or more transmitters released from one nerve terminal  But still most neurons release only a single amino acid or amine neurotransmitters Cholinergic Neurons:  Acetylcholine (ACh)- is the neurotransmitter at the neuromuscular junction and therefore is synthesized by all the motor neurons in the spinal cord and brain stem  ACh synthesis requires a specific enzyme, choline acetyltransferase (ChAT)  ChAT is manufactured in the soma and transported to the axon terminal like all presynaptic proteins  Only cholinergic neurons contain ChAT, therefore this enzyme is a good marker to identify cells that use ACh as it’s neurotransmitter  ChAT synthesizes ACh in the cytosol of the axon terminal, and the neurotransmitter is concentrated in synaptic vesicles by the actions of an ACh transporter o ChAT transfers an acetyl group from acetyl CoA to choline o Source of choline is the extracellular fluid, where it exists in low micromolar concentrations o Choline is taken up by the cholinergic axon terminals via specific transporter o Because the availability of choline limits how much ACh can be synthesized in the axon terminal, transport of choline into the neuron is said to be the rate-limiting step in ACh synthesis  Rate-limiting Step- in a biochemical reaction that leads to the production of a chemical, the one step that limits the rate of synthesis.  Cholinergic neurons also manufacture the ACh degradative enzyme acetylcholinesterase (AChE) o AChE is secreted into the synaptic cleft and is associated with cholinergic axon terminal membranes o AChE is also manufactured by some noncholinergic neurons, so this enzyme is not as useful a marker for cholinergic synapses as ChAT  AChE degrades ACh into choline and acetic acid o This happens very quickly because AChE has one of the fastest catalytic rates among all known enzymes  Inhibition of AChE prevents the breakdown of ACh, disrupting transmission at cholinergic synapses on skeletal muscle and heart muscle o Deaths from the irreversible inhibition of AChE is typically a result of respiratory paralysis Catecholaminergic Neurons  Amino acid tyrosine is the precursor for three different amine neurotransmitters that contain a chemical structure called a catechol  These neurotransmitters are called catecholamines o Catecholamine neurotransmitters are:  Dopamine (DA)  Norepinephrine (NE)  Epinephrine (Adrenaline)  Catecholaminergic neurons are found in regions of the nervous system involved in the regulation of movement, mood, attention, and visceral function  All catecholaminergic neurons contain the enzyme tyrosine hydroxylase (TH), which catalyzes the first step in catecholamine synthesis, the conversion of tyrosine to a compound called dopa  Activity of TH is rate limiting for catecholamine synthesis  The enzyme’s activity is regulated by various signals in the cytosol of the axon terminal  End-product inhibition- decreased catecholamine release by the axon terminal causes the catecholamine concentration in the cytosol to rise  Dopa is converted into the neurotransmitter dopamine by the enzyme dopa decarboxylase o Dopa decarboxylase is abundant in catecholaminergic neurons, so the amount of dopamine synthesized primarily depends on the amount of dopa available  Neurons that use norepinephrine (NE) as a neurotransmitter contain, besides TH and dopa decarboxylase, they contain the enzyme do
More Less

Related notes for PSY2116

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.