CNS Neurotransmitters

Question 1

Presynaptic Inhibition

Answer 1

Some CNS nerve terminals synapse on other (excitatory) pre-synaptic terminals; an action potential in the inhibitory terminal releases GABA, which opens chloride channels in the target pre-synaptic terminal and ‘short-circuit’ the action potential in the excitatory terminal, reducing the number of voltage-gated Ca2+ channels that open in response to the action potential; thus, less excitatory neurotransmitter is released

Question 2

Spatial summation

Answer 2

Many excitatory inputs converge on a target and fire action potentials simultaneously; each individually small synaptic potential summates, driving the post-synaptic membrane potential toward threshold

Question 3

Temporal summation

Answer 3

A single excitatory input stimulated in succession causes a larger EPSP due to synaptic facilitation (Ca2+ accumulation)

Question 4

Function of ACh in the CNS

Answer 4

Coordinated movement and cognitive functions (motivation, memory, and learning)

Question 5

Pathophysiological Role of ACh in CNS

Answer 5

Alzheimer’s Disease
Parkinson’s Disease
Schizophrenia

Question 6

Synthesis of Dopamine

Answer 6

Tyrosine is convered into L-Dopa by Tyrosine Hydroxylase (TH); L-Dopa is converted to Dopamine

Question 7

Synthesis of Serotonin

Answer 7

Tryptophan is converted to 5-OH-tryptophan by Tyrosine Hydroxylase; 5-OH-tryptophan is then converted to Serotonin (5-HT)

Question 8

Storage of monoamines

Answer 8

Transmitter is taken up into the storage vesicle via the vesicular monoamine transporter (VMAT)

Question 9

Monoamine oxidase (MAO)

Answer 9

Enzymatically destroys dopamine, norepinephrine, and serotonin

Question 10

Termination of monoamine signaling

Answer 10

Synaptic activity of monoamines is terminated mainly by pre-synaptic membrane transporters: dopamine transporter (DAT), norepinephrine transporter (NET), serotonin transporter (SERT)

Question 11

Function of Dopamine in CNS

Answer 11

Initiation of voluntary movement
Reward related behaviors
Working memory
Attention

Question 12

Function of NE in the CNS

Answer 12

Arousal, attention, vigilance
Sleep-wake cycle
Fear, anxiety
Mood/emotion

Question 13

Function of Serotonin in the CNS

Answer 13

Arousal, attention, sleep
Processing of sensory information
Emotion, mood regulation
Eating/drinking behaviors

Question 14

Pathophysiological role of Dopamine in CNS

Answer 14

Schizophrenia
Parkinson’s Disease
OCD
ADHD

Question 15

Pathophysiological role of NE in CNS

Answer 15

Mania
Depressio
Anxiety disorders
ADHD

Question 16

Pathophysiologic role of Serotonin in CNS

Answer 16

Depression
Anxiety
Schizophrenia

Question 17

Synthesis of GABA

Answer 17

GABA is synthesized from Glutamate via glutamic acid decarboxylase (GAD)

Question 18

Termination of GABA signaling

Answer 18

Primarily reuptake into the pre-synaptic nerve terminal and surrounding glial cells by the GABA transporter

Question 19

GABA(A) Channel - Function

Answer 19

Ionotropic; GABA binding opens ligand-gated Cl- channel, decreasing neuronal excitability via ISPs

Question 20

GABA(B) Channel - Function

Answer 20

Metabotropic; Gi/o coupled, inhibits adenylyl cyclase, decreases Ca2+ conductance, opens K+ channel

Question 21

Pathophysiological Role of GABA in CNS

Answer 21

Generalized anxiety disorder
Seizure disorders
Sleep disorders
Alcohol withdrawal

Question 22

Synthesis of Glutamate

Answer 22

Glutamate is formed from Glutamine by the action of glutaminase in the nerve ending

Question 23

Glutamate termination and storage

Answer 23

Released glutamate either re-enters the neuron via neuronal glutamate transporter [(Gt(n)] or is taken up by the glial cell transporter [(Gt(g)] and is converted to glutamine by glutamine synthetase (GluSyn)

Question 24

Pathophysiological Role of Glutamate in CNS

Answer 24

Epilepsy
Ischemic brain damage
Addiction
Schizophrenia