• Remember that neurotransmitters are released from axon terminals, bind to another neuron’s dendrite to pass on a message, then are taken back up by the terminal button

Agonists

• Agonists are copies of neurotransmitters

• They produce more or create an enhanced effect of what a neurotransmitter usually does

• They supply more of that neurotransmitter so it can do it’s job at a higher rate

• Dendrites have specific binding sites that only accept certain neurotransmitters

  • Although these chemicals are not literally the same thing, they can still fit into the receptor site

Examples

Opiates

• These are agonists for endorphins, our natural pain killers

• They create pain relief

• Highly addictive

Dopamine Agonists (L-Dopa)

• Supply more dopamine

• Often prescribes for those with Parkinson’s and RLS

• These can stop tremors

Antagonists

• Antagonists block neurotransmitters in one of two ways

  • They can bind to the receptor site without activating it, taking up that space and not allowing the neurotransmitter to pass its message

  • They can block the terminal and not allow neurotransmitters to be released into the synapse

• They cause less of or diminish entirely the effect that the neurotransmitter caused

Examples

Botulinum Toxin (Botox)

• A antagonist for acetylcholine, which contracts muscles

• Blocks the release of ACh, meaning muscles cannot contract

• Localized paralysis

Alcohol

• An antagonist for glutamate

• This means it is a depressant: depressing reaction time, judgement, foresight, etc.

Reuptake Inhibitors

• Reuptake Inhibitors (R.I.) block the neurotransmitter from being absorbed back into the axon terminal

• This means that the neurotransmitters continue to float in the synapse and bind with dendrites

• These drugs increase the effect that the neurotransmitter caused

Examples

S.S.R.I.

• Selective Serotonin Reuptake Inhibitors do not allow serotonin chemicals to reenter the axon terminal

• This keeps it in the synapse where it continues to bind to dendrites

• This can help regulate mood and other processes

  • Remember that serotonin regulates many different things throughout the body