Voltage gated channels

Question 1

How to isolate sodium channels

Answer 1

Replace intracellular potassium with caesium and add cadmium And tea to external

Question 2

Sodium conductance characteristics

Answer 2

Activation Threshold -40 mV
Sigmoidal increase with voltage
Half Max -25 mV

Question 3

Potentially what explains stimulus dependent decrease of nerve evoked EPSP?

Answer 3

Slow recovery from sodium channel inactivation

Time constant 20 ms accelerated with membrane hyper polarisation

Question 4

What does ciguatoxin do to neuronal excitability?

Answer 4

Increases neuronal excitability and causes spontaneous opening of single sodium channels by shifting voltage of activation to more negative potentials

Question 5

How do you isolate calcium channels?

Answer 5

Inhibit sodium currents with TTX or replace external sodium with an impermeable cation, and suppress potassium currents with intracellular caesium and/or extracellular TEA

Question 6

The affect of barium on calcium channels

Answer 6

1.5 fold increase in current density

Question 7

Calcium conductance characteristics

Answer 7

Activation threshold -30 MV, sigmoidal increase with depolarisation, Half max -5 MV

Question 8

Effect of barium on calcium activation curve

Answer 8

Shifted 10 mV to more negative potentials

Question 9

Which sodium channels are present?

Answer 9

TTX sensitive Nav1.1-1.3,1.7

Question 10

Which types of calcium channels are present?

Answer 10

L, N, P/Q and R

Question 11

What’s the L type molecular identity and antagonist?

Answer 11

Cav1.2 and Dihydropyridines (eg nifedipine)

Question 12

What is the N type molecular identity and antagonist?

Answer 12

Cav2.1 and omega conotoxin gvia

Question 13

What is the PQ identity and antagonist?

Answer 13

Cav2.2 and omega conotoxin mviic

Question 14

What is R type identity and antagonist?

Answer 14

Cav2.3 and nickel ions

Question 15

What potassium channels are present?

Answer 15

Kv, A, BKCa, AHP, Kir, Katp, M

Question 16

What is the Kv type identity and antagonist?

Answer 16

Kv1.5,1.6, and TEA, verapamil

Question 17

What is that IA type identity and antagonist?

Answer 17

kv3.x, kv4.x, 4 aminopyridine

Question 18

What is the AHP antagonist?

Answer 18

Ryanodine

Question 19

What is the KiR identity and antagonist?

Answer 19

Kir2.x, Kir3.x, Barium

Question 20

What is the KATP identity and antagonist?

Answer 20

Kir6.x/Sur1-2, glibenclamide

Question 21

What is the M type identity and antagonist?

Answer 21

KCNQ1-5, XE991 (linopirdine)

Question 22

What is the H type identity and antagonist?

Answer 22

HCN1-4, caesium etc

Question 23

Main calcium channel which is target different neuro transmitters?

Answer 23

N type

Question 24

What is IKv called and what is its function?

Answer 24

Delayed outward rectifier, terminate action potential rapidly.

Question 25

Delayed outward rectifier conductance characteristics

Answer 25

Activation threshold -40 mV, increase with voltage until saturation about 20 mV

Question 26

What is the Potassium current IA called and what is its function?

Answer 26

Transient outward current, activated in sub threshold range of neuronal excitation and functions to reduce the excitatory effects of depolarising stimuli by decreasing rate of decay of AHP

Question 27

What are the effects of 4-AP?

Answer 27

Inhibits transient outward current IA responsible for AHP decay, increase firing frequency

Question 28

What is iKca and what is it function?

Answer 28

Calcium dependent potassium current , Hyperpolarise cell after burst of action potentials sufficient to raise intra cellular Calcium

Question 29

What is Ikir and what is its function?

Answer 29

Inward rectifying current, hyperpolarisation activated. Outward current blocked by intracellular magnesium. Maintain resting membrane potential

Question 30

What is iKca and what is it function?

Answer 30

Calcium dependent potassium current , Hyperpolarise cell after burst of action potentials sufficient to raise intra cellular Calcium

Question 31

What is IkATP and what is it function?

Answer 31

ATP sensitive potassium current, transduce changes in cell metabolism to membrane potential. Open at low ATP concentration.

Question 32

What is IM and what is it function?

Answer 32

Muscarine sensitive, noninactivating potassium current. Partially activated at rest. ACh evokes slow depolarisation associated with increased membrane resistance and decreased outward current resulting from inhibition of IM.