(11) Type I & II Receptors

type I receptors

Ionotropic Receptor / Ligand Gated Ion Channels

cell membrane

type I receptors are found in __

milliseconds (fastest)

onset of type I receptors

GABA_A receptors

• Cl^- channels

• inhibitory effect

• drugs:

Benzodiazepines

• “zepam”, “zolam”

• enhance frequency of chloride channel opening

barbiturates

• “barbital”, “bital”, “tal”

• enhance the duration of chloride channel opening

Nicotinic receptors

• Na⁺ channels

• excitatory effect

• drugs: antagonist

curare derivatives

• - curiums, -curoniums

• skeletal muscle relaxant

type II receptors

• 7-transmembrane receptors

• serpentine receptors

• G-protein Coupled Receptors

• metabotropic receptors

• most abundant

• found in the cell membrane

seconds

onset of type II receptors

G-protein

• acts as an on-off switches for cell signaling

• stimulation or inhibition results in the modulation of the enzyme system responsible for producing the following transduction components, secondary messengers

Adenylate Cyclase (AC) system

uses cAMP as a second messenger

Gs

• Activates AC system

• increase cAMP concentration

Gi

• inhibits AC system

• decrease cAMP concentration

Gq

activates PLC system

IP3 and DAG

PLC system enhance the production of __

contraction

increase of Ca²⁺

regulation of ion channel

control ion channels without second messengers

Muscarinic ACh receptors
Opioid receptors

Open K⁺ channels thus enhance K⁺ permeability