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Neuropharmacology
A.5
Some neurotransmitters excite nerve impulses in postsynaptic
neurons and others inhibit them
• Neurotransmitters (Excitatory)
a. Released from the presynaptic neuron
into the synaptic cleft.
b. Bind to receptors in the post synaptic
neuron causing channels to open.
c. This depolarizes the neuron triggering
an action potential.
• Some neurotransmitters inhibit an action
potential which inhibits nerve impulses.
Nerve impulses are initiated or
inhibited as a result of summation
• One pre-synaptic neuron usually does not
trigger an action potential.
a. Can be hundreds or even thousands of
presynaptic neurons.
• Summation- the combined effects of
excitatory and inhibitory neurotransmitters.
a. Action potential depends on the
balance of these two.
Many different slow-acting neurotransmitters modulate fast
synaptic transmission in the brain
• Neuromodulators- slow acting
neurotransmitters that take many milliseconds
to have an effect.
a. Usually affect groups of neurons.
b. Ex. Dopamine and serotonin
1. Dopamine deficiency is linked to
Parkinson’s Disease.
2. Serotonin is linked with
depression, OCD, and anxiety.
Memory and learning involve changes in neurons caused by slow
acting neurotransmitters
• Secondary messengers- promote synaptic
transmission
a. Increase the amount of receptors.
b. Chemically modify the receptors to
increase the speed.
c. Can last for days and cause long-term
potentiation (LTP).
Psychoactive drugs affect the brain by either increasing or
decreasing post-synaptic transmission
• Psychoactive Drugs:
1. Excitatory
a. Increase post synaptic transmission.
b. Ex, Cocaine, nicotine
2. Inhibitory
a. Decrease postsynaptic transmission.
b. Ex: Alcohol, THC
Stimulant drugs mimic the stimulation provided by the
sympathetic nervous system
• Stimulants- drugs that promote the activity of
the nervous system.
a. Increase heart rate, blood pressure.
b. Make the body respond as though it is
being stimulated by the sympathetic nervous
system.
Addiction can be affected by genetic predisposition, social
environment and dopamine secretion
• Three areas affecting addiction:
a. Genetic predisposition
1. Genes increase chances
a. Gene DRD2 codes for dopamine
receptors.
1. People with one allele
consumed more alcohol.
b. Social environment:
1. Peer pressure, poverty
c. Excess dopamine production
1. Dopamine is associated with feelings of well
being and pleasure.