Neurotransmitter Regulation

10 Questions

What is the primary characteristic of an inverse agonist?

It produces an effect opposite to that of an agonist

Which type of antagonist is characterized by a right shift of the dose-response curve?

Competitive antagonist

What is the term for the maximum response of a drug that can be achieved, even with high doses?

Efficacy

Which type of receptor regulation occurs when a receptor is chronically exposed to an agonist?

Downregulation

What is the term for the ratio of the dose of a drug that produces toxicity to the dose that produces a therapeutic effect?

Therapeutic index

What is the primary characteristic of a non-competitive antagonist?

It has a different binding site than the agonist

What is the term for the phenomenon where not all receptors need to be occupied to produce a maximal response?

Spare receptors

What is the primary characteristic of a partial agonist?

It has high affinity but submaximal efficacy

Which type of antagonist is characterized by an unsurmountable antagonism?

Non-competitive antagonist

What is the primary characteristic of a receptor upregulation?

An increase in the number of receptors

Study Notes

Ion Channels and Transporters

Ion channels (Na+, K+, Ca++) are affected by drug binding, which inhibits the transport of transmitters.
Transporters are involved in the transport of transmitters and can be affected by enzyme stimulation (e.g., Pyridoxine increases Decarboxylase activity).

Enzyme Interactions

Enzyme stimulation can increase the activity of specific enzymes (e.g., Decarboxylase).
Enzyme inhibition can occur through competitive (e.g., AChE inhibitors) or non-competitive (e.g., COX inhibition) mechanisms.

Receptors

Receptors are macromolecular components of the cell (usually proteins, but can be nucleic acids) that interact with drugs to produce a response.
They are usually present on the surface or inside the cell.
Receptors help determine qualitative differences in drug responses and the quantitative relationship between drug concentration and effects.

Classification of Receptors

G-protein coupled receptors, enzyme-linked receptors, and intracellular receptors are the three main types of receptors.
Ion channels are also a type of receptor.

Receptor Characteristics

Recognition site: a specific region of the receptor that recognizes the specific drug molecule.
Affinity: the ability of a drug to bind to a receptor.
Intrinsic activity (efficacy): the ability of a drug to provoke a response after binding to a receptor.

Efficacy and Potency

Efficacy is the maximum effect produced by a drug after combining with the receptor.
Potency is the amount of drug required to produce a desired effect.
Drugs with greater efficacy are more therapeutically useful, while drugs with higher potency require lower doses.

Dose-Response Curve

The dose-response curve determines the relationship between the dose administered and the extent of response produced by a drug.

Ligands

Agonists: produce a response by binding to receptors.
Antagonists: do not produce a response and can be used to block receptor sites.
Types of agonists: full agonist, partial agonist, inverse agonist.
Types of antagonists: competitive, non-competitive.

Competitive Antagonists

Bind to the same site as agonists.
Resemble agonists chemically.
Cause a right shift of the dose-response curve.
Can be surmounted by increasing the agonist dose.

Non-Competitive Antagonists

Bind to a different site than agonists.
Do not resemble agonists chemically.
Cause a flattening or downward shift of the dose-response curve.
Can be unsurmountable.

Therapeutic Index

Therapeutic index (TI) is the ratio of TD50 (toxic dose) to ED50 (effective dose).
TI helps compare the safety of two drugs.

Receptor Regulation

Receptor occupancy: the more receptors occupied by the drug, the greater the pharmacodynamic response.
Receptor up- and down-regulation: chronic exposure to an antagonist leads to upregulation, while chronic exposure to an agonist leads to downregulation.