Postsynaptic Response

What type of signaling is neurocrine?

merocrine and paracrine

post-synaptic steps (chemical gated ion channels)

• rapid, short-acting synaptic potential

  1. ion channels open (Na+ in OR more K+ out and Cl- in)

  2. causes EPSP (depolarization) or IPSP (hyperpolarization)

post-synaptic steps (binding to G-protein-coupled receptor)

• NT bind and activate second messenger pathwayy

• alters the open state of ion channels

• ion channels close

  • less Na+ in (IPSP)

  • less K+ out (EPSP)

• slow synaptic potentials and long-term effect

ligand-gated channels

• opens channels

• fast synaptic transmissions (<100ms)

• receptor and channel part of the same protein

• little amplification (one or two NT opens one channel)

• ionotropic receptor (receptor = the channel)

G-protein coupled receptor

• slow synaptic transmissions (>100ms)

• opens or closes ion channels, among other things

• receptor and channels are SEPARATE proteins

• amplification (one NT may affect many channels)

• metabotropic receptor (activates second massagers)

What is the postsynaptic response determined by ?

by the receptor, NOT the neurotransmitter

“nicotinic” acetylcholine receptor

• ionotropic receptor that acetylcholine must bind to

• non-selective cation channel

• mainly causes depolarization

“muscarinic” acetylcholine receptor

• metabolic/ G-protein coupled receptor

• can link indirectly to K+ channels

• cause hyperpolarization

hyperpolarizing

E_x < V_rest

depolarizing

E_x > V_rest

generalization (to all ion channels)

• opening of NT receptors drives V_m towards E_x for that channel

• depending on the E_x, the effect many be inhibitory or excitatory

inhibitory (IPSP)

• E_x < threshold

• membrane more negative to rest

excitatory (EPSP)

• E_x > threshold

• membrane more positive to rest