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Fundamental Neurobiology > neurotransmitters > Flashcards

neurotransmitters Flashcards

1
Q

overview of direct synaptic transmission

A

neurotransmitter release -> receptor binding -> ion channels open or close -> conductance change causes current flow -> postsynaptic potential changes (EPSP or IPSP) -> summation and threshold -> action potential or no action potential

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2
Q

3 features of transmitters

A
  1. presence in presynaptic neuron
  2. calcium dependent release when presynaptic neuron depolarizes
  3. specific receptors for the substance must be present on the postsynaptic cell
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3
Q

dale’s principle

A

thought that one nerve was only responsible for releasing one neurotransmitter
proven wrong

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4
Q

3 basic groups of neurotransmitters

A

“classic” low-molecular weight
gases
neuropeptides

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5
Q

life cycle of neurotransmitter

A
  1. synthesis
  2. storage
  3. release
  4. postsynaptic effects
  5. inactivation
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6
Q

classic low-molecular weight/small-molecule transmitters

A

synthesized in axon terminals, packaged in small vesicles, and stored there until release

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7
Q

gases

A

synthesized in nerve terminals
cannot be stored in cells
highly lipid and water soluble

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8
Q

neuropeptides

A

synthesized in soma
processed and packaged in large dense-core vesicles in the Golgi
transported to axon terminal

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9
Q

steps of transmitter release

A

presynaptic depolarization -> Ca2+ entry -> transmitter release
- vesicles fuse with plasma membrane and release contents into synaptic cleft via exocytosis

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10
Q

ionotropic

A

direct

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11
Q

metabotropic

A

indirect

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12
Q

3 mechanisms of inactivation of neurotransmission

A
  1. diffusion
  2. degradation
  3. reuptake (into glia, or nerve terminals), not for neuropeptides
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13
Q

acetylcholine

A
  • most comes from septal nuclei and basal forebrain
  • important for learning, memory, and other cognitive processes (attention and decision making)
  • evolved defense that targets Ach transmission
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14
Q

ach agonist

A

nicotine
- highly reinforcing, calming, increases concentration

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15
Q

ach antagonist

A

scopolamine
- muscarinic antagonist, prevents the ability of medial temporal lobe structures to encode memory

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16
Q

acetylcholinesterase/cholinesterase

A

enzyme that breaks down ach

17
Q

alzheimer’s disease

A

one cause is a reduction of cholinergic neurons in the midbrain, leading to reduced availability of ach in the mediation of memory processes
also characterized by accumulation of neurofibrillary tangles or extracellular plaques that are insoluble and block the projection of cholinergic projections

18
Q

structure of metabotropic receptors

A

have similar transmembrane structure as ionotropic receptors but lack pores to conduct ions
instead ligand binding triggers intracellular signaling via g-proteins

19
Q

areas of the brain more involved with neurotransmission

A

mostly in striatum and frontal cortex

20
Q

tracing of neurotransmitters

A
  • neurons using a specific transmitter can be identified by the presence of the transmitter itself, or tagging proteins involved in any step of its life cycle
  • mapping by immunohistochemistry and fluorescence probe-tagging, then imaging with electron microscopy
  • radio-labeled probes (autoradiography) following in situ hybridization with antisense oligonucleotides for certain receptor subunits
21
Q

critical excitatory and inhibitory transmitters

A
  • gamma-aminobutyric acid (GABA)
  • glycine
  • glutamate
22
Q

glutamate

A
  • primary excitatory transmitter in the brain
  • synthesis: mostly derived from glutamine taken into the presynaptic terminal
  • storage: vesicular glutamate transporters (VGLUT) load glu into synaptic vesicles
  • inactivation: clearance from synaptic cleft by reuptake proteins (GLAST, EAAT, GLT-1, mostly into glial cells)
23
Q

ionotropic glutamate receptors

A

NMDA, AMPA, kainate

24
Q

metabotropic glutamate receptors

A

8 members in 3 classes

25
Q

gamma-aminobutyric acid (GABA)

A
  • primary inhibitory transmitter
  • synthesis: from glutamate via glutamic acid decarboxylase with pyridoxal phosphates as a co-factor
  • storage: transporters bring into synaptic vesicles
  • release: at inhibitory synapses, many are interneurons, but the primary projection neurons in the cerebellum and striatum use GABA
  • inactivation: high-affinity transporters in presynaptic terminals and glia
26
Q

biogenic amines (monoamines)

A

regulate many brain functions and are also active in the pns
involved in mood and affect motivation, attention, and arousal
neurons releasing them are typically localized into small groups in the brainstem

27
Q

catecholamines

A

made of a catechol and amine
- epinephrine, norepinephrine, dopamine
- synthesis: in presynaptic terminals (enzymes arrive via axonal transport, precursors are generally taken up directly by presynaptic terminals)
- storage: usually small clear vesicles
- release: calcium dependent vesicle fusion
- receptors: metabotropic
- inactivation: enzymatic degradation and re-uptake transporters

28
Q

dopamine

A

dopamine neurons are localized in the brainstem structures substantia nigra and ventral tegmental area

29
Q

dopamine neurons respond to

A
  1. unexpected delivery of reward
  2. cues that precede rewards
  3. pause when expected rewards do not occur
    - reward prediction error
30
Q

norepinephrine

A

involved in wakefulness, attention and feeding behaviors
localized in the midbrain and send widespread and diffuse projections to much of the rest of the brain
respond to alerting stimuli

31
Q

epinephrine

A

localized in brainstem/midbrain/thalamus

32
Q

5-hydoxytryptamine (5-HT)/serotonin

A

involved in sleep, wakefulness and mood
localized in the pons and upper brainstem, widespread functions to the forebrain
- synthesis: 2 step process starting with tryptophan in the brainstem
- storage: vesicles
- inactivation: uptake by specific serotonin transporter
- receptors: one ionotropic, multiple metabotropic, target of hallucinogens such as LSD

33
Q

antagonists of ATP

A

caffeine
theophylline

34
Q

5 categories of peptide neurotransmitters

A
  • brain-gut peptides (substance P: pain)
  • opioid (enkepahlin, endorphins: analgesia, euphoria)
  • pituitary (vasopressin, oxytocin: bonding, lactation)
  • hypothalamic (LH: sex)
  • miscellaneous (Neuropeptide Y: energy balance, eating)
35
Q

endocannabinoids

A

heavily expressed in striatum (motivation), substantia nigra (dopamine neurons), hippocampus (memory and spatial location), cerebellum (movement)
- unconventional bc: postsynaptic release, non-vesicular, receptors are pre-synaptic

Fundamental Neurobiology (16 decks)

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