pharmacology, drugs and therapeutics

what are selective agonists

drugs that activate only some adrenoreceptors

SALBUTAMOL - BETA 2 AGONIST - treatment of asthma

what are selective antagonists

drugs that block only some adrenoreceptors

PROPANOLOL - BETA 1 AND 2 ANTAGONIST - treatment or arrhythmia

transmembrane signalling

transfer of information across the plasma membrane
some signalling molecules = lipid soluble so can cross lipid bilayer
bind to intracellular receptors in cytosol - effect produced

cell surface receptors

hydrophilic signalling molecules have to bind to receptors on cell surface

4 categories of cell surface receptors

receptor channels --> ionotropic receptors

G protein coupled receptors --> G proteins involved

receptor enzymes --> intrinsic enzyme activity

integrin receptors --> interactions with cytoskeleton

G protein coupled receptors

may couple to adenylyl cyclase

- cAMP second messenger

- regulates protein kinase A activity

may couple to phospholipase C

- IP3- and DAG second messengers

- release Ca2+

- regulates protein kinase C activity

sources of intracellular calcium

internal stores via IP3- or Ca2+ --> stimulated release from endoplasmic reticulum

Ca2+ channels

inhibition of Ca2+ out cell

effects of Ca2+

affects target protein directly

binds to calmodulin - activates target protein

works via some other Ca2+ binding protein

what is a drug

any chemical that affects a biological system

what is a receptor

drug binding site

receptors examples

cell surface receptors

intracellular

ion channels

carriers

enzymes

nucleic acids

function of drug receptors

responsible for selectivity of drug action through specific interactions with macromolecules

drug bound to only one receptor

small response

drug bound to few receptors

bigger response

drug bound to all receptors

large response

drug bound to all receptors with excess drug molecules

maximum (saturated) response

define affinity

The strength of attraction between drug and receptor

low Ec50

high affinity

define efficacy

the ability to produce a desired or intended result

what is efficacy determined by

affinity

full agonist

high affinity and high efficacy

partial agonist

high affinity and lower efficacy

antagonist

high affinity and low/no efficacy

relationship between agonist concentration and effect in body

as drug concentration increases, response rises to maximum until all receptors are saturated