S2 Neuro Exam 1: Synaptic Transmission 2

Front 1

Define the criteria for accepting a substance as a (classical) neurotransmitter

Back 1

1. localization- localized to the presynaptic element & present w/i presynaptic neuron
2. release- released from presynaptic element upon activation of terminal & depolarization of neuron
3. identity- action on target cells is same as effects on presynaptic neuron by transmitter

Front 2

Describe the distribution of Glutamate

Back 2

-most prevalent fast excitatory transmitter in CNS
-used by about 1/2 neurons in brain

Front 3

Describe the synthesis of Glutamate

Back 3

Its derived from a-ketoglutarate by GABA transaminase, which is also a precursor for the inhibitory neurotransmitter g-aminobutyric acid (GABA).
-derived from glutamine & converted to glutamate & ammonia by mitochondria

Front 4

Describe the inactivation mechanisms of Glutamate

Back 4

-reuptake directly by presynaptic terminal transporters
-indirectly through astrocyte transporters
-converted back to glutamine & transported back to terminal

Front 5

Describe the functions of Glutamate

Back 5

-role in learning & memory
-Ca2+ ion entry through NMDA activated channels in ischemic tissue
^can exacerbate injury & increase cell death
-associated w/ excitotoxicity

Front 6

Describe the distribution of GABA

Back 6

-primary inhibitory neurotransmitter in brain
-found in high amnts in substantia nigra stratum, lentiform nuclei, hypothalmus, hippocampus, periaqueductal gray

Front 7

Describe the synthesis of GABA

Back 7

-GABA is synthesized from glutamate by glutamic acid decarboxylase.

-It is also converted from glutamine-->glutamate
--> GABA

Front 8

Describe the inactivation mechanisms of GABA

Back 8

The recycling mechanisms are therefore similar to glutamate, except for the additional step of conversion back to glutamate from glutamine in both neurons and astrocytes.

Front 9

Describe the functions of GABA

Back 9

-transmitter for Purkinje cells of cerebellum
-linked to chloride ion channels, usually hyperpolarizes, occasionaly excitatory
-associated w/ drug effects: anesthetics, caffeine, alcohol

Front 10

What AA neurotransmitter is implicated in epilepsy, bipolar disorder, schizophrenia, & anxiety disorders

Back 10

GABA

Front 11

Describe the distribution of Acetylcholine

Back 11

-in CNS & PNS
-CNS: motor & preganglionic autonomic neurons use it.
-excitatory & inhibitory properties
-ionotropic & metabotropic receptors.
-broadly projecting ACh systems that are part of conscious arousal.

Front 12

Describe the synthesis of Acetylcholine

Back 12

synthesized from choline and acetyl Coenzyme A by choline acetylase

Front 13

Describe the inactivation mechanisms of Acetylcholine

Back 13

After release, acetylcholine is broken down by acetylcholinesterase to choline and acetic acid. Both components are transported into the terminal and recycled

Front 14

Describe the functions of Acetylcholine

Back 14

involved in diverse functions from memory to muscle contraction

Front 15

What does the loss of acetylcholine containing neurons in the nucleus basalis (brain) lead to?

Back 15

Alzheimer's disease

Front 16

Describe the distribution of Dopamine & Norepinephrine

Back 16

-throughout nervous system
-both excitatory & inhibitory

Front 17

Describe the synthesis of Dopamine & norepinephreine

Back 17

tyrosine-->dopamine-->norepinephrine

Front 18

Describe the inactivation mechanisms of Dopamine & norepinephrine

Back 18

-inactivation and recycling by catechol-O-methyl transferase (COMT) on the post synaptic membrane and monoamine oxidase (MAO) in the presynaptic terminal cytoplasm.

Front 19

Describe the functions of Dopamine & norepinephrine

Back 19

-modulate consciousness, sleep, & motor activity in brain
-motor functions, rewarding behaviors/addiction

Front 20

Why are most of the enzymes involved in this pathway significant?

tyrosine-->dopamine-->norepinephrine
-->epinephrine

Back 20

tyrosine--(amino acid hydrolase)--> DOPA
DOPA--(dopa decarboxylase)--> dopamine
dopamine--(dopamine b-hydroxylase)--> NE
NE--(phentolamine N- methytransferase)--> EPI

*are modifiable by pharmocologic or toxic agents.

Front 21

What neurotransmitter is involved in Parkinson disease?

Back 21

dopamine

Front 22

Many antipsychotic drugs have their primary actions on ____________ receptors

Back 22

catecholamine

Front 23

Describe the distribution of serotonin

Back 23

excitatory & inhibitory

Front 24

Describe the synthesis of serotonin

Back 24

synthesized from tryptophan by subsequent actions of tryptophan hydroxlase, and 5-hydroxytryptophan decarboxylase.

Front 25

Describe the inactivation mechanisms of serotonin

Back 25

-broken down by monoamine oxidase and or transported back into the presynaptic terminal.

Front 26

Antidepressents work through inhibiting the reuptake of ____________ or through inhibiting monamine oxidases (MAOI)

Back 26

serotonin (SSRIs)

Front 27

Describe the functions of serotonin

Back 27

- sleep/wake cycles, emotional behavioral states & prominent component of platelets (vasoconstriction).
-associated with the action of may hallucinogens (LSD, mescaline, ecstasy).

Front 28

Describe the distribution of histamine

Back 28

-excitatory
-component of mast cells and basophils (vasodilation) and involved in gastric secretion.

Front 29

Describe the synthesis of histamine

Back 29

synthesized from histidine by histidine decarboxylase.

Front 30

Describe the inactivation mechanisms of histamine

Back 30

-broken down by histamine N methyltransferase and diamine oxidase.
Antihistamines are generally receptor blockers.

Front 31

Describe the functions of histamine

Back 31

Centrally, it is associated with sleep/wake cycles an the maintenance of a conscious state

Front 32

Describe the properties of neuropeptides in the CNS

Back 32

-located in the CNS and PNS
*substance P, b-endorphin, enkephalins and vasoactive intestinal polypeptide (VIP).
-all metabotropic and G-protein coupled
-Release is often non-synaptic or as a co-transmitter
-Centrally, neuropeptides are prominent in the hypothalamus, also found in the brainstem and basal ganglia.
*oxytocin & vasopressin

Front 33

Describe the functions of neuropeptides in the CNS

Back 33

-many have primary functions related to enteric nervous system
-major roles in autonomic function (oxytocin, vasopressin)
-pain (substance P)
-pain/pleasure (b-endorphin & enkephalon)
-circadian rhythm (VIP)

Front 34

Describe the properties of purines in the CNS

Back 34

-ATP & Adenosine are synthesized & recycled through the same pathways for energy metabolism in mitochondria.
-ATP is often a co-transmitter packaged with other neurotransmitters (noradrenaline & neuropeptide Y)

Front 35

Describe the functions of purines in the CNS

Back 35

-released from sympathetic perivascular nerve fibers and act on vascular smooth muscle, constricting or relaxing depending on receptor
-act on purine autoreceptors to effectively regulate their own release and that of any cotransmitter

Front 36

Describe the properties of nitric oxide as a transcellular messenger in the CNS

Back 36

-gasotransmitters
-interact as cotransmitter
-sympathetic enzymes present in neurons of brain

*Nitric oxide responses are mediated through a cGMP mechanism in both neurons and neuroglia

Front 37

Describe the functions of nitric oxide as a transcellular messenger in the CNS

Back 37

-mediate numerous effects in body tissue particularly related to vascular smooth muscle.
- a neuromodulator at the synaptic level in both a feed forward and feedback (retrograde) regulation of synaptic activity.

Front 38

Describe the properties of endocannabinoids as a transcellular messenger in the CNS

Back 38

-synthesized from arachidonic acid derivatives
-degraded by fatty acid amide hydrolase and monacylglycerol lipase.
-act through two primary receptors CB1 (nervous system, and organs) and CB2 (immune system

Front 39

Describe the functions of endocannabinoids as transcellular messenger in the CNS

Back 39

-In the nervous system, modulate synaptic transmission as a retrograde feedback effect.
-effect physiological processes associated w/ appetite, pain sensation, mood and memory

Front 40

What is retrograde transmission?

Back 40

-proccess of feedback from postsynaptic cell
-postsynaptic cell responds to synaptic activation by releasing a second chemical messenger capable of affecting the presynaptic nerve terminal or neuron.

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