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