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Neurotransmitters

Neurotransmitters. Monoamines as Neurotransmitters. Monoamine Neurotransmitters Monoamines are regulatory molecules derived from amino acids. CATECHOLAMINES : these are tyrosine derivatives: dopamine , norepinephrine, epinephrine . Bind to adrenergic receptors .

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Neurotransmitters

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  1. Neurotransmitters

  2. Monoamines as Neurotransmitters

  3. Monoamine Neurotransmitters • Monoamines are regulatory moleculesderived from amino acids. • CATECHOLAMINES: these are tyrosinederivatives: dopamine, norepinephrine, epinephrine. Bind to adrenergicreceptors. • Norepinephrine is a neurotransmitter and hormone but epinephrine is primarily a hormone tyrosine tyrosine Other monoamines:2) SEROTONIN (derived from tryptophan) 3) Histamine (derived from histidine)

  4. Norepinephrine as a neurotransmitter • Used in both the CNS and PNS • Sympathetic neurons use norepinephrine on smooth muscles, cardiac muscles, and glands. • Used by neurons of the CNS in brain regions associated with arousal • Amphetamines work by stimulating norepinephrine pathways in the brain.

  5. Monoamine Action and Inactivation KNOW THISPATHWAY

  6. Monoamines use G-protein Coupled Channels THIS IS A SECONDMESSENGER SYSTEM This is a BETA ADRENERGIC receptor. Sympathetic neurons of the PNS use norepinephrine as their neurotransmitter.

  7. Serotonin as a neurotransmitter Used by neurons in the raphe nuclei (middle region of brainstem) • Implicated in mood, behavior, appetite, and cerebral circulation • The drug LSD and other hallucinogenic drugs may be agonists. • Serotonin specific reuptake inhibitors (SSRIs) are used to treat depression. • Prozac, Paxil, Zoloft serotonin

  8. Dopamine as a neurotransmitter • Neurons that use dopamine (dopaminergic neurons) are highly concentrated in the midbrain in two main areas: • Nigrostriatal dopamine system: involved in motor control • Mesolimbic dopamine system: involved in emotional reward dopamine

  9. Nigrostriatal dopamine system: (motor) • Parkinson disease is caused by degeneration of these neurons. • Patients are treated with L-dopa and monoaminoxidase inhibitors • Activates the substantia nigrabrain region. dopamine

  10. involved in emotional reward. • Schizophrenia is associated with too much dopamine. • Dopamine antagonists are used to treat schizophrenia • Activates the limbic system. • Associated with addictions to nicotine, alcohol, other drugs Mesolimbic dopamine system dopamine

  11. Cocaine • Abused because it elevates energy/mood • Crosses the blood-brain barrier • In mesolimbic reward system, it is a triple-reuptake inhibitor: • Blocks reuptake of dopamine • Blocks reuptake of serotonin • Blocks reuptake of norepinephrine • Danger: • Blocks Na+ ion channels • Raises heart rate/blood pressure • Increase risk of stroke, seizure

  12. Other Neurotransmitters

  13. Amino acids as NTs • Excitatory NT – glutamate and aspartate • Glutamate – major excitatory neurotransmitter • Produces EPSPs in 80% of synapses in cortex • Constitutes major energy use in the brain • Involved in memory • Astrocytes take glutamate from the synaptic cleft to maintain homeostasis glutamate

  14. Inhibitory NTs Glycine • produces IPSPs • Binding of glycine opens Cl− channels, causing an influx of Cl−. • Makes it harder to reach threshold • Important in the spinal cord for regulating skeletal muscle movement. • This allows antagonistic muscle groups to relax while others are contracting • (e.g. biceps relax while triceps contract).

  15. GABA , another inhibitory neurotransmitter • Gamma-aminobutyric acid • most common neurotransmitter in the brain • used by 1/3 of the brain’s neurons. • inhibitory, opens Cl− channels • involved in motor control. Degeneration of GABA-secreting neurons in the cerebellum results in Huntington disease.

  16. GABA receptors contain a chloride channel

  17. Nitric Oxide • Nitric oxide (not nitrous oxide laughing gas) • A gas produced by some neurons in the CNS and PNS from the amino acid L-arginine • Diffuses across the presynaptic axon plasma membrane (no vesicle) • Diffuses into the target cell and activates the production of cGMP as a second messenger • Causes blood vessel dilation (Viagra works by stimulating theaction of nitric oxide) and helps kill bacteria • May also act as a retrograde NT

  18. Summation: Spatial Spatial summation occurs due to convergence of signals onto a single postsynaptic neuron. All of the EPSPs and IPSPs are added together at the axon hillock.

  19. Summation: Temporal Temporal summation is due to successive waves of neurotransmitter release that add together at the initial segment of the axon.

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