Pharmacology of the Nervous System Flashcards
What is pharmacology?
Study of chemical substances that interact with a specific target within a biological system to produce a physiological effect
Describe the effects of heroin + where, why and how these effects are produced
Produces euphoria, analgesia and cough suppression. Analgesic effect produced when drug interacts with peri-aqueductal grey region, euphoria when targets the ventral tegmental area and cough suppression with solitary nucleus – all in the brainstem. Drug binds to opioid receptors to produce effects.
What is the function of opioid receptors?
Binds exogenous compounds such as drugs and is found across a wide range of areas in the brain and body.
How do drugs act to produce side effects?
On other targets in the same tissue or other tissues, On the same target in other tissues, Dependent on the dose of drug administered
What are desired drugs?
Those where there is a large difference in the dose required to induce the desired effect and the dose required to induce side effects/adverse effects
What are the 4 common drug targets and how do drugs act?
- Ion channels 2. Transport proteins 3. Enzymes 4. Receptors. Drugs act to ENHANCE ACTIVATION (stimulate an effect) or PREVENT ACTIVATION (block and effect being produced).
What are 4 most common prescribed drugs used around the world?
- Atorvastatin – Enzyme (statin most commonly prescribed. This acts on an enzyme called HMG Co A Reductase)
- Amlodipine – Ion Channel (acts on calcium channel which is useful for hypertension, as causes vasodilation reducing BP)
- Salbutamol – Receptor (binds to a receptor – beta 2 adrenergic receptor in lungs leading to bronchodilation making breathing easier)
- Citalopram – Transport Protein (antidepressant which acts on selective serotonin reuptake inhibitors – block serotonin from being taken up again)
Why is selectivity important for drugs to be effective therapeutic agents?
Selectivity is more important to drugs than endogenous compounds because neurotransmitters are very specifically delivered to their drug targets as they would only be released by a nerve into a synapse where only receptors sensitive to that particular neurotransmitter are present. However, most drugs are administered orally and hence they need to circulate in bloodstream to reach tissue of interest – however, this means they can go anywhere in the body and so activate/block a wider range of similar looking receptors in different places in the body. Hence the best drugs display a high level of selectivity to a particular drug target.
Define side effect
Effect produced by a drug which is secondary to the intended effect. If it has negative health consequences, it would be an adverse effect.
Describe off-target side effects
This is also known as the lock and key effect. Example is Pramipexole, commonly used against Parkinson’s disease. Drugs such as Pramipexole, which is a dopamine receptor agonist at low dosage, will fit dopamine receptors as it is the best fit however, serotonergic effects can also be seen since it is structurally similar enough to fit into a serotonin receptor. At higher doses, although drug is not perfect fit, enough of alternative receptor channels are opened for its effects to be seen so the larger the dose, the more pronounced the side effects. Lose selectivity when dose is increased.
Describe on-target side effects
Acts on same target site but in a different tissue producing an effect which wasn’t the intended for which the drug was taken. Analgesia, euphoria, cough suppression (different effect produced by heroin binding to opioid receptors in different tissues) – not all of these would be the intended effect.
