Neurotransmitter Classification

Question 1

neurotransmitters are classified based on

Answer 1

• chemical nature
• response they elicit
• their receptors mechanism of action

Question 2

how is the activity of a neurotransmitter changed?

Answer 2

regulated by changing the rates of synthesis and release at the synapse, and by blocking reuptake and degradation

Question 3

what is the endocannainoid system

Answer 3

a group of endogenous cannabinoid receptors located in the mammalian brain and throughout the central and peripheral nervous systems, consisting of neuromodulatory lipids and their receptors

Question 4

list criteria necessary to be a nt

Answer 4

• synthesis in the neuron
• storage within nerve ending
• release in response to stimulus
• bonding and recognition at post synaptic cell
• mechanism for inactivation and termination of activity

Question 5

name some neuromodulators

Answer 5

• NO
• adenosine
• neurosteroids
• polyamines
• lipids

Question 6

how are nt released?

Answer 6

(A) In the resting state, vesicles are attached to microtubules.
(B) When an action potential is received, calcium channels open. (C) Vesicles move to the plasma membrane, and (D) bind to a complex of docking protein
(E) Neurotransmitter is released, and
(F) vesicles are recycled

Question 7

name amine nts

Answer 7

Ach, norepinphrine, epinephrine, dopamine, 5-HT

Question 8

name amino acid nts

Answer 8

glutamate GABA

Question 9

Name purine nts

Answer 9

ATP, adenosine

Question 10

name gase nts

Answer 10

NO

Question 11

name peptide nts

Answer 11

endorphons, tachykinins

Question 12

name lipid nts

Answer 12

anandamide, 2-AG (arachidony glycerol)

Question 13

excitatory nts

Answer 13

Acetylcholine 
Aspartate 
Dopamine 
Histamine 
Norepinephrine 
Epinephrine 
Glutamate 
Serotonin

Question 14

inhibitory nts

Answer 14

GABA
Glycine
Anandamide
2-AG

Question 15

fast mode nts use

Answer 15

ionotropic receptors

Question 16

modulatory mode nts use

Answer 16

GPCR (metabotopic receptors)

Question 17

how is Ach synthesized

Answer 17

in cholinergic neurons, by choline acetyltransferase. you need choline and acetyl coA as reactants

Question 18

where is Ach released and why

Answer 18

Motoneurons at the level of the neuromuscular junction (muscle contraction)
Pre-ganglionic neurons of the sympathetic nervous system and parasympathetic post-ganglionic neurons (slowing of the heart rate, bronchoconstriction, stimulation of intestinal smooth muscle)
Neurons of the reticular system (wakefulness, sleep-wake transition)
Cholinergic synapses of basal ganglia (learning, memory)

Question 19

what are the 2 cholinergic receptors

Answer 19

• nicotinic (ionotropic):
• Nm depolarization of NMJ
  -Nn activation of post ganglionic neurons
• muscarininc receptors (metabotropic)
  -M1: Depolarization of autonomic and CNS neurons
  – M2 Negative inotropic and chronotropic effects on the heart
  – M3 Stimulate sweat, bronchial, salivary and gastric acid secretion; increase NO production from vascular endothelium and vasorelaxation

Question 20

how to remove Ach from synaptic cleft

Answer 20

• ACh released from synaptic vesicles is hydrolyzed to choline and acetate by acetylcholinesterase (AChE), an enzyme that is localized in the synaptic cleft. Choline is a poor binder of the cholinergic receptors, however is taken up by the uptake system on the presynaptic membrane
• The remainder of ACh (i.e., that has not been hydrolyzed by acetylcholinesterase) is taken back up into the pre-synaptic nerve by specific transporters (reuptake).

Question 21

explain ACHe

Answer 21

is an enzyme which hydrolyses Ach, its active site contains 2 subsites. An anionic subsite to bind Ach to the enzyme. The esteratic subsite where the hydrolytic action occurs, releasing acetate and choline

Question 22

list the 3 ionotropic glutamate receptors

Answer 22

AMPA
NMDA
KAINATE

Question 23

GABA-a receptors are

Answer 23

ionotropic, and ligand gated Chloride channels

Question 24

GABA-b receptors are

Answer 24

metabotropic

Question 25

benzodiazepines bind to

Answer 25

GABA-a, cause a potentiation of the response to endogenous GABA; these drugs reduce anxiety and also cause muscle relaxation

Question 26

barbiturates bind to

Answer 26

GABA-a, stimulate them directly in the absence of GABA; because of this lack of dependence on endogenous ligand, they are more likely to cause toxic side effects in overdose.

Question 27

how is GABA re-uptaken?

Answer 27

by plasma membrane transporters (symports): GABA transporters 1-3 (GAT-1, GAT-2, GAT-3) Betaine-GABA transporter-1 (BGT-1) (GAT1-3 in brain, BGT-1 mostly in kidney but also present in brain)

Question 28

where is glycine found? what does it do? what kind of receptor is it?

Answer 28

- inhibotry nerons in spinal cord - where it blocks impulses travelling down the cord in motor neurons - ionotropic. And is blocked by strychinine. They are ligand gated chloride channels.

Question 29

all catecholamines (dopamine, nor-/epinephrine) are derived from?

Answer 29

tyrosine. | They are biogenic amines. They are released through varicosities along the axon not only the end of it.

Question 30

where is epinehrine produced

Answer 30

adrenal medulla

Question 31

L-DOPA in melanocytes is the precursor or

Answer 31

melanins

Question 32

norepinephrine is the major transmitter in

Answer 32

sympathetic nervous system, in post ganglionic neurons. for fight or flight. Also in the brainstem, for overall awareness or attention (locus ceruleus)

Question 33

amphetamines

Answer 33

have stimulatory effects since they increase the concentration of catecholamines in the synaptic cleft

Question 34

epinephrin traits

Answer 34

- influences heart, lung - redirection of blood to skeletal muscle - stimulatory effects on glycogen metabolism in liver - is not essential for life

Question 35

dopamine traits

Answer 35

- nerves that interconnect the nuclei of the basal ganglia in the brain and control voluntary movement - damage causes parkinsons - schizophrenia - causes vasodilation and used for treatment of renal failure - found in the nigrostriatal tract

Question 36

how are catelcholamines catabolised?

Answer 36

- half life of 1 min - Monoamine oxidase (MAO): catecholamines by oxidative deamination to yield the corresponding aldehyde. Catechol-O-methyltransferase (COMT) also inactivates catecholamines by methylation using S-adenosylmethionine (SAM) as the one-carbon donor. MAO inhibitors and methamphetamine block catecholamine degradation, allowing their accumulation in the presynaptic neuron and subsequent leakage into circulation, providing an antidepressant action.

Question 37

serotonin

Answer 37

aka 5-HT - Trp hydrolase need cofactor BH4 - 5-HT is converted to serotonin by DOPA decarboxylase - in raphe nuclei, more active when awake - involved in feeding, sexual behavior, temperature

Question 38

how is serotonin broken down?

Answer 38

- oxidation by monoamine oxidase | - dehydration: aldehyde deydrogenase

Question 39

NO

Answer 39

- in ANS and enteric NS is made from arginine by BH4 NOS. - excessive NO= alzheimers and parkinsons - is not stored in vesicles but released immediately