Neurotransmitters and Drugs (Pt 2 of 2)
antagonist
drug that blocks or impedes the normal activity of a given neurotransmitter
agonist
drug that mimics or strengthens the effects of a neurotransmitter
Agonists are
chemicals that mimic a neurotransmitter at the receptor site and, thus, strengthen its effects EX: Parkinson's disease, a progressive nervous system disorder, is associated with low levels of dopamine. Therefore, a common treatment strategy for Parkinson's disease involves using dopamine agonists, which mimic the effects of dopamine by binding to dopamine receptors.
Cocaine has two effects on synaptic transmission: it impairs reuptake of dopamine and it causes more dopamine to be released into the synapse. Would cocaine be classified as an agonist or antagonist? Why?
As a reuptake inhibitor, cocaine blocks the normal activity of dopamine at the receptor. The function causing more dopamine to be released into the synapse is agonist because it mimics and strengthens the effect of the neurotransmitter. Cocaine would be considered an agonist because by preventing the enzymatic degradation of the neurotransmitters, it increases the potential time that these neurotransmitters might be active in the synapse.
psychotropic medication
Drugs that treat psychiatric symptoms by restoring neurotransmitter balance
Psychoactive drugs can act as
agonists or antagonists for a given neurotransmitter system
psychotropic medications
are drugs that treat psychiatric symptoms by restoring neurotransmitter balance.
terminal button:
axon terminal containing synaptic vesicles
An antagonist
blocks or impedes the normal activity of a neurotransmitter at the receptor. EX Certain symptoms of schizophrenia are associated with overactive dopamine neurotransmission. The antipsychotics used to treat these symptoms are antagonists for dopamine—they block dopamine's effects by binding its receptors without activating them. Thus, they prevent dopamine released by one neuron from signaling information to adjacent neurons.
In contrast to agonists and antagonists, which both operate by
by binding to receptor sites, reuptake inhibitors prevent unused neurotransmitters from being transported back to the neuron. This allows neurotransmitters to remain active in the synaptic cleft for longer durations, increasing their effectiveness.
semipermeable membrane
cell membrane that allows smaller molecules or molecules without an electrical charge to pass through it, while stopping larger or highly charged molecules
neuron
cells in the nervous system that act as interconnected information processors, which are essential for all of the tasks of the nervous system
neurotransmitter
chemical messenger of the nervous system
membrane potential
difference in charge across the neuronal membrane
action potential
electrical signal that moves down the neuron's axon
threshold of excitation
level of charge in the membrane that causes the neuron to become active
reuptake
neurotransmitter is pumped back into the neuron that released it
all-or-none:
phenomenon that incoming signal from another neuron is either sufficient or insufficient to reach the threshold of excitation
Selective serotonin reuptake inhibitors (SSRIs) are drugs that
prevent unused neurotransmitters from being transported back to the neuron.
receptor
protein on the cell surface where neurotransmitters attach
synapse
small gap between two neurons where communication occurs
synaptic vesicle
storage site for neurotransmitters
resting potential
the state of readiness of a neuron membrane's potential between signals
biological perspective
view that psychological disorders like depression and schizophrenia are associated with imbalances in one or more neurotransmitter systems
hyperpolarization
when a cell's charge becomes more negative than its resting potential
depolarization
when a cell's charge becomes positive, or less negative