Receptors 1

Receptor

The component of the organism with which the chemical agent is presumed to interact

__ are the most important drug targets

Receptors

Most receptors are __

proteins

Protein structure - primary

the amino acid sequence

Protein structure - secondary

beta sheets and alpha helices

protein structure - tertiary

3D intractions

Protein structure - quaternary

interaction of several proteins

The 4 types of receptors

Intracellular - steroid receptors

receptor tyrosine kinase - growth factor receptors

ligand-gated ion channels - Nicotinic AchR

GPCRs - Adrenergic and muscarinic receptors

Receptors: Sympathetic NS

short cholinergic preganglionic

nicotinic receptor in the synapse

long adrenergic postganglionic

(Adrenergic + Muscarinic sweat glands)

Receptors: PSNS

long cholinergic preganglionic

nicotinic receptor in the synapse

short cholinergic postganglionic

(muscarinic)

Receptors: Somatic NS

Long cholinergic neuron

activates Nicotinic muscle receptors

(nicotinic)

Alpha-bungarotoxin

neurotoxin found in snake venom

binds to nicotinic AChR and blocks the receptor

progressive paralysis

Epibatadine

toxic alkaloid secreted by the skin of tree frogs

Binds very tightly to Nicotinic AChR and activates the receptor

Spams followed by paralysis

Membrane potential is the result of

uneven ion distribution across the membrane

selective permeability of certain ions

Resting membrane potential

-70 millivolts

How does nicotinic receptor activation translate into cell response?

Opening of nAChR leads of influx of sodium ions (depolarization of membrane potential)

When the membrane depolarizes above a certain threshold level, voltage-sensitive Na+ channels are triggered to open, causing more influx which initiates action potential

Tetrodotoxin

Potent neurotoxin found in liver and sex organs of pufferfish

Binds and blocks voltage-sensitive sodium channels

no action potential - paralysis

starts with GI symptoms