SM38/39

Question 1

There are 6 ionotropic receptors - 4 excitatory ligand-gated channels and 2 inhibitory ligand-gated channels. What are the NTs associated with each?

Answer 1

Excitatory:

1. Acetylcholine-nicotinic
2. Serotonin-5HT-3 receptors
3. Glutamate (AMPA/Kainate/NMDA)
4. ATP P2X receptors

Inhibitory:

1. GABA (gamma-amino butyric acid)
2. Glycine

Question 2

______ receptor channels open non-selective cation channels and _____ receptor channels open chloride channels

Answer 2

Excitatory, Inhibitory

Question 3

What type of receptor?

• Takes less than 1/3 of millisecond from binding of agonist to detection of electrical response of the ion channel
• Appears as barrel with multiple staves
• Alpha subunits are common to all of these receptors and are essential for binding of agonist

Answer 3

Ligand gated ion channels (AKA ionotropic receptors)

Question 4

What are the four CYS loop receptor types

Answer 4

Ach nicotinic, Serotonin 5HT-3, GABAa, Glycine

Question 5

Nicotinic ACh receptors initiate _____

Answer 5

skeletal muscle contraction, ganglionic transmission, and many excitatory functions in the CNS

Question 6

Serotonin 5HT-3 receptors mediate _____

Answer 6

excitation, concentrated in CNS sites associated with emetic response

Question 7

“___-setrons” (e.g. Ondansetron) competitively inhibit _______ receptors. What is this used to treat?

Answer 7

5HT-3 receptors, used to treat nausea and vomiting (especially in cancer patients on chemotherapeutic agents)

Question 8

________ is a uncompetitive antagonist of GABA receptors, blocking Cl- channel once the channel is opened by GABA

Answer 8

Penicillin

Question 9

The use of benzos as positive allosteric modulators occurs on which receptor type?

Answer 9

Cys-loop GABAa receptors

Question 10

Disease due to mutation in alpha subunit of the glycine receptor

Answer 10

Familial Startle Disease aka Hyperekplexia

Question 11

Unique facts of the cys-loop glycine receptor

Answer 11

1) only major inhibitory transmitter in spinal cord and 2) only NT that acts exclusively on ligand-gated channels (the others act on GPCRs as well)

Question 12

Differences between NMDA receptor and AMPA receptor (both types of glutamate receptors)

Answer 12

NMDA receptors are glutamate gated calcium channels that facilitate learning and memory. NMDA receptors have Mg2+ stuck in the channel and is responsive to both glutamate and depolarization. NMDA channels need glycine to be fully activated

AMPA receptors are glutamate-gated Na+ channels that mediate fast synaptic transmission in the CNS

Question 13

Excitotoxicity and Alzheimers

Answer 13

Disorder in NMDA receptors, where too much calcium enters the cell. Memantine is a therapeutic agent that is an open channel blocker of NMDA receptors

Question 14

P2X ATP receptors are involved in ___ and appear in abundance in ___

Answer 14

every stage of wound healing; diseased urinary bladder

Question 15

What type of receptor?

• act via secondary and tertiary messenger substances
• Two essential components: the receptor, the GTP-binding protein
• Receptor crosses membrane 7 times and when bound, changes conformation –> activation of GTP binding protein

Answer 15

GPCRs aka metabotropic receptors

Question 16

Galpha-s for ___ pathways and Galphaq for ___ pathway

Answer 16

PKA (via cAMP generation), PKC (via PLC activation)

Question 17

“Venus Flytrap” appearing GPCRs

Answer 17

Metabotropic glutamate receptors (mGluRs) and GABA-b receptors

Question 18

With the exception of ____, all of the receptor agonists that are ligands for membrane ionic channels also activate GPCRs

Answer 18

glycine

Question 19

Three kinds of receptor tyrosine kinase / transmembrane enzymes

Answer 19

GF receptors (e.g. epidermal growth factor), Insulin receptors, Cytokine receptors

Question 20

These receptors must be in a dimerized configuration before signaling can ensue

Answer 20

Transmembrane enzymes aka receptor tyrosine kinases (RTKs)

Question 21

Insulin RTKs make use of which two pathways?

Answer 21

1. Primarily, the metabolic PI-3-kinase/AKT/mTOR pathway; 2. Secondarily, the growth RAS/MAPkinase pathway (this is more heavily in use by growth factor RTKs)

Question 22

Why are cytokine receptors not technically RTKs?

Answer 22

The cytokine receptor is not a transmembrane protein kinase, but it is a receptor with an attached intracellular kinase –> acts in an RTK-like fashion

Question 23

Distinguish between tachyphylaxis and desensitization

Answer 23

Desensitization is the decrement of response in the continued presence of the drug; Taxhyfdalfa is a decline in response due to acute repeated injections with shortened intervals between injections