PSL300H1 Lecture 4: PSL300 - CMP Lecture 4 Notes
Lecture 4 Notes
âą Post synaptic receptors
o Transmitter diffuses across synapse and binds to receptor in postsynaptic membrane,
causing change in shape of receptor protein
o Receptor determines effect, not transmitter
o Ionotropic (directly open channel)
âȘ Ligand binding opens an ion channel
âȘ Transmitter binding to post synaptic membrane changes potential, called Post
Synaptic Potential (PSP) causing ion channel to open
âȘ Ion channel may be specific for cation (Na+, K+): EPSP (depolarizing)
âą EPSP: excitatory postsynaptic potential
âą Change in MP of postsynaptic cell after influx of positively charged ions
(depolarization) triggering activation of ligand sensitive channel
âȘ Ion channel may be specific for Cl- or K+ ion: IPSP (hyperpolarizing)
âą IPSP: inhibitory postsynaptic potential
âą Change in MP of postsynaptic cell after influx of negatively charged ions
(hyperpolarization) making neuron less likely to generate AP
âȘ Ligands for ionotropic receptors (neurotransmitters)
o Acetylcholine (Ach)
o Glutamate
o GABA
o Glycine
âą Can all act on metabotropic receptors but itâs the receptor that
determines effect and not transmitter
o Metabotropic (initiates metabolistic cascade to activate enzymes)
âȘ Ligand binding to post synaptic metabotropic receptor activates enzyme thatâs
usually G-protein coupled
âȘ Enzyme facilitation results in increase production or destruction of 2nd
messenger, cAMP, cGMP, InP3
âȘ 2nd messenger activates other enzymes; phosphokinase, which phosphorylates
other proteins (membrane or cytoplasm)
âȘ Phosphorylates membrane proteins (ion channels), results in modulation of ion
currents
âą Phosphorylation is a metabolic effect, and the MP will develop slowly
(slow ESPS, slow IPSP)
âą Slow change due to enzyme activity it must go through first before
influencing ion channels
âȘ B-Adrenoreceptor
âą Receptor for noradrenalin (NA), binding activates adrenylyl cyclase via G
protein alteration
o Increases production of cAMP which then activated kinases
o Phosphorylates membrane Ca++ channels, increases Ca++ influx
âȘ Ligands for Metabotropic Receptors
