psychoactive drugs Flashcards
what does the term psychoactive drugs mean?
drugs that act on the brain and produce changes in perception, mood, consciousness and behaviour
what is a receptor
protein molecules whose function is to recognise and respond to endogenous chemical signals
what is a ligand
a molecule/ atom that binds reversibly to a protein
what is an agonist?
drug which activate receptors
what is an antagonist?
a drug that binds to the receptor without causing activation
what is affinity of a drug?
how well a drug binds to a receptor
what is efficacy of a drug?
how well a drug once bound to a receptor elicits a response
what is the potency of a drug?
a measure of the amount of drug required to elicit a response of a given intensity
what are reversible antagonists?
they compete w/ agonist binding typically at the same site -> binds reversibly
what are irreversible (covalent) antagonists
binds irreversibly to receptor -> may change the conformation of the receptor to reduce ability of agonist to bind
what are orthosteric sites?
the primary ligand binding site of a receptor
what are allosterc site?
a site that’s distinct from the endogenous ligand
what are ionotropic receptor and examples
ligand gated ion channels
what are metabotropic receptor and examples
receptors that couple through secondary messenger and can indirectly regulate ion channel opening e.g ACh receptor, Muscarinic, GPCR
what are generic features of ligand gated ion channels
- typical heteromeric assemblies of 4/5 subunits
- each subunit has transmembrane spanning helices -> form a central aqeuous channel
- ligand binding -> channeling opening -> milliseconds
what is the process of GPCR when activated?
1- ligand binding induces GDP -> GTP exchange on the Gα subunit
2 - Gα subunit dissociates from βγ complex
3 - Gα subunit and βγ complex activate downstream targets
4 - when bound to target GTPase -> Gα subunit is increased leads to -> hydrolysis of GTP to GDP
what downstream effectors are activated by stimulation of GPCRs
adenyl cyclase -> cAMP formation, phospholipases, kinases -> MAPK,PI3K, ion channels, gene transcription -> via MAPK, PKA/CREB
what steps happens when kinase linked receptors are activated?
1 - ligand binding leads to dimerization of receptors
2 - receptor dimers undergo autophosphorylation at Tyr residues
3 - pTyr sites recruit proteins w/ SH2 domains -> leads to activation of downsteam signalling
how are cytokine receptors regulated?
by endogenous negative feedback mechanisms
examples of nuclear (hormone) receptors
glucocorticoid receptor, oestrogen receptor, androgen receptor
what is the key fast excitatory transmitter in the CNS
glutamate
what are the key fast inhibitory transmitter in the CNS?
G amino butyric acid (GABA) & glycine
what are some ionotropic glutatmate receptor examples
AMPA, kainate, NMDA receptors
what are some metabotropic glutatmate receptor examples
grp 1, grp 2 and grp 3
what are some ionotropic GABA receptor examples
GABA a & GABA c
what are some metabotropic GABA receptor examples
GABA b
