4.2 physiology of GABA and Glycine Receptors

Question 1

describe GABA C receptor

Answer 1

-ionotropic and activates a Cl- channel (let’s Cl- go into cell) -Only found in the retina.

Question 2

which 2 receptor types don’t belong with the others? ACh, glutamate, GABA, glycine, ATP, serotonin receptors.

Answer 2

1. ATP has its own Ligand-gated ion channel gene family 2. glutamate has its own gene Ligand-gated ion channel family 3. all the others share the same Ligand-gated ion channels gene superfamily

Question 3

what’s the difference between GABA A/glycine receptors and ACh nicotinic receptors? Why do these receptors signal different effects (i.e. why do the channels have different ion selectivity)?

Answer 3

these receptors are similar but the amino acids lining the pore of the channel are different: 1. ACh: negatively charged. 2. GABA A/Glycine are + charged

Question 4

name some compounds that activate GABA A. why do they have different effects ?

Answer 4

1. general anesthetics, benzodiazepines (antianxiety agents and muscle relaxants), barbiturates and alcohol 2. There are different GABA(A) subtypes types and different agents can bind selectively to different subtypes

Question 5

name 2 effects of the GABA found in interstitial fluid that constantly provides low-level activation of GABA A receptors

Answer 5

1.Cuts down on the noise in the brain. 2. Increases the signal-to-noise ratio in the brain.

Question 6

is glycine excitatory?

Answer 6

it can be. 2. Glycine can bind to NMDA receptors and make them more sensitive to glutamate

Question 7

where’s glycine found?

Answer 7

mainly found in the brainstem and spinal cord

Question 8

glycine can also be inhibitory. how do we know this?

Answer 8

strychnine antagonizes glycine. Strychnine antagonizes the direct inhibition provided by glycine and leads to convulsions and muscular hyperactivity

Question 9

how is glycine removed from synaptic cleft?

Answer 9

Glycine is taken back into the presynaptic terminal by a glycine transporter

Question 10

what happens to ions in this EPSP?

Answer 10

They travel down their concentration gradient, depolarizing the cell

Question 11

during IPSP, does the cell depolarize or hyperpolarize? which way does K+ go? Cl-?

Answer 11

• K+ will leave cell
• Cl- will enter cell

Effect is hyperpolarization

Question 12

1. define reversal potential.
2. what is K+ reverse potential?
3. when K+channels open, and K+ moves, is this more consitently stimulatory or inhibitory?

Answer 12

1. “when you open a channel, the ion will flow to attempt to reach reversal potential”
2. -80mv
3. Opening K+ channels is more consistently inhibitory

Question 13

what happens when GABA activates a Cl- receptor in a pt in early development? 3. How does trend change over time to rectify this problem?

Answer 13

1. Early in development, Cl- is moved into the cell by a Na-K-Cl cotranporter
2. now the [Cl-] is higher inside the cell -> when GABA receptor opens Cl- channel, the Cl- leaves the cell (opposite of adults)
3. The K+/Cl- cotransporter is not expressed in early development (this pump wouldkeep Cl- out of the cell)

Question 14

what are the 3 types of inhibitory synapses in the spinal cord?

Answer 14

–Ones that use GABA
–Ones that use glycine
–Ones that use both GABA and glycine