Ionotropic receptors

Question 1

explain nicotinic Ach receptor

Answer 1

• 5 binding sites: 2 alpha, 1 beta, 1 delta, 1 gamma
• each subunit has 4 transmembrace segements; M2 lines the pore
• 2 Ach molecules open the channel by binding to the alpha subunits: opens for 1msec

Question 2

explain and draw GABAa receptor

Answer 2

• 5 glycoprotein subunits: 2 alpha, 2 beta, 1 gamma
• 4 transmembrance segements M2 lines pore
• 2 GABA molecules open the channel by binding to the sites between alpha and beta subunits
• opens for chloride anions (Cl-)

Question 3

explain glutamate receptor

Answer 3

• 4 subunits
• each subunit has 3 transmembrane segment; M2 is a reentrant pore loop
• each subunit has a bidining site
• N-terminal tail and extracellular loop b/w M3 and M4 channel opens when two binding sites are occupied

Question 4

What are the 3 main types of glutamate ionictropic receptors

Answer 4

1. AMPA
   - heterotetrameric: means 4, not all the same
   - dimer: consists of two identical subunites
   - GluA1, GluA2,Glu3, GluA4
   - 4 glutamate binding sites but channel will open with 2 bound
   - Na+ and K+ pass freely
   - presence of GluA2 prevent passage of CA2+
2. Kainate receptors
   - 5 receptor subunits (GluK1-5)
   - Na+ and K+ pass freely, low permability for Ca2+
   - slower EPSPs compared to AMPA receptors
3. NMDA receptors
   - 3 subunits (GluN1-3)
   - heterotetramers with 2 GluN1 and 2 GluN2
   - 2 glutamate (N2) and 2 glycine (N1) binding sites
   - Na+ K+ and Ca2+ is peremable
   - partially voltage dependent