Transcript What neurotransmitters have been identified?

Psychology 304:
Brain and Behaviour
Lecture 15
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Announcement
I will hold additional office hours in preparation for the
midterm exam:
Friday, October 15:
3:30 - 4:30 PM
Monday, October 18: 11:30 AM - 1:00 PM
Tuesday, October 19: 10:00 AM - 12:00 PM
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From last class ....
Smooth Muscle Tissue
Last class, some students suggested that smooth
muscle tissue is subject to voluntary control.
Researchers unequivocally describe smooth muscle
tissue (found in blood vessels, the iris, the
gastrointestinal tract, the respiratory tract, etc.) as
subject to involuntary control.
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Smooth muscle tissue is innervated by the autonomic
nervous system.
If you are interested in obtaining a reference regarding
this point, please see me after class.
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Transmission of Electrochemical Neural Signals and
Neuropharmacology
1. How do neurotransmitters generate electrochemical
signals in postsynaptic neurons?
2. What mechanisms terminate synaptic transmission?
3. What neurotransmitters have been identified?
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By the end of today’s class, you should be able to:
1. distinguish between ionotropic and metabotropic
receptors.
2. describe the processes of reuptake and enzymatic
degradation.
3. distinguish between classes of neurotransmitters in
terms of function and location.
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How do neurotransmitters generate electrochemical
signals in postsynaptic neurons? (continued)
Metabotropic receptors (MRs): (continued)
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Figure A
Figure B
Metabotropic Receptor Activity
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What mechanisms terminate synaptic transmission?
• Two mechanisms terminate synaptic transmission:
1. Reuptake.
Neurotransmitters are repackaged into vesicles in
the cystoplasm (i.e., pinocytosis).
2. Enzymatic degradation.
Example: Acetylcholinestrase.
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Mechanisms of Neurotransmitter Deactivation
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What neurotransmitters have been identified?
• Four classes of small-molecule neurotransmitters have
been identified:
1. Acetylcholine (ACh)
 One of the most widespread neurotransmitters.
 Found at neuromuscular synapses, synapses in the
autonomic nervous system, and synapses in parts of
the central nervous system.
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 Associated with movement, autonomic function,
learning, and memory.
 Deficiency associated with Alzheimer’s disease.
2. Monoamine neurotransmitters
 Found in neurons whose cell bodies are largely
located in the brain stem. These neurons give rise to
an enormous number of terminal buttons distributed
throughout many brain regions.
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 Subdivided into two groups:
(a) Catecholamines:
 Dopamine: associated with movement, attention,
reinforcement/reward, verbal learning, and
planning.
Deficiency associated with Parkinson’s disease
and ADHD.
Excessive levels associated with schizophrenia.
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Production of the Catecholamines
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 Epinephrine (adrenalin): associated with
attention and arousal.
 Norepinephrine (noradrenaline): associated with
attention, arousal, mood, feeding, and sexual
behaviour.
Deficiency associated with
depression.
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(b) Indoleamines:
 Serotonin: associated with mood, sleep, feeding,
sexual behaviour, and pain.
Deficiency associated with
depression.
 Melatonin: associated with sleep.
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3. Amino acid neurotransmitters
 Found in fast-acting neurons in the central nervous
system.
 Include glutamate, gamma-aminobutyric acid
(GABA), glycine, and aspartate. Of these,
glutamate and GABA are most important:
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 Glutamate: the principle excitatory
neurotransmitter in the brain and spinal cord;
associated with learning and memory.
Deficiency associated with
impaired performance on learning
tasks
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 GABA: the principle inhibitory neurotransmitter in the
brain and spinal cord; associated with mood and the
“seizure threshold.”
Deficiency associated with
anxiety disorders and
seizures.
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4. Soluble gas neurotransmitters
 Include nitric oxide (NO) and carbon monoxide (CO).
 Unconventional neurotransmitters. After production in
the cytoplasm, they immediately diffuse through the
presynaptic cell membrane. Thereafter, the diffuse
through the postsynaptic cell membrane and stimulate
the production of a second messenger.
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 Function as retrograde transmitters: Diffuse back to
the presynaptic neuron and regulate its activity.
 Little is known about the functions of CO. NO is
associated with autonomic activity, learning, and
memory.
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• Large-molecule neurotransmitters are neuropeptides:
 Found largely in neurons of the CNS.
 Include five categories: pituitary peptides,
hypothalamic peptides, brain-gut peptides, opioid
peptides, and miscellaneous peptides.
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Transmission of Electrochemical Neural Signals and
Neuropharmacology
1. How do neurotransmitters generate electrochemical
signals in postsynaptic neurons?
2. What mechanisms terminate synaptic transmission?
3. What neurotransmitters have been identified?
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