Neurotransmission in the ANS
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Questions and Answers

What role does the vesicle-associated transporter (VAT) play in the transport of ACh?

  • It transports ACh from the vesicle to the cytoplasm.
  • It facilitates the uptake of ACh from the cytoplasm into vesicles. (correct)
  • It converts ACh into inactive metabolites.
  • It synthesizes ACh from its precursors.

    • Which enzyme is responsible for converting Dopa into Dopamine?

  • Dopamine-β-hydroxylase
  • Dopa decarboxylase (correct)
  • Tyrosine hydroxylase
  • Catechol-O-methyltransferase

    • What triggers the exocytosis of vesicles containing ACh at the nerve terminal?

  • The binding of ACh to post-synaptic receptors
  • The influx of Ca²⁺ through voltage-gated Ca²⁺ channels (correct)
  • The inflow of Na⁺ through sodium channels
  • The activation of G-proteins in the presynaptic terminal

    • What is the process by which Noradrenaline (NA) is synthesized within the vesicle?

    <p>Dopamine is converted to NA by dopamine-β-hydroxylase.</p> Signup and view all the answers

    What type of carrier is involved in the transport of Tyrosine into the presynaptic nerve terminal?

    <p>A Na⁺ dependent carrier</p> Signup and view all the answers

    What is the primary enzyme responsible for the synthesis of acetylcholine in the nerve terminal?

    <p>Choline acetyltransferase (ChAT)</p> Signup and view all the answers

    Which of the following best describes how neurotransmitter action is terminated in the synapse?

    <p>Metabolism or neuronal reuptake</p> Signup and view all the answers

    During cholinergic transmission, what is the role of the choline transporter (CHT)?

    <p>To transport choline into the nerve terminal</p> Signup and view all the answers

    Which neurotransmitter is primarily associated with non-adrenergic, non-cholinergic (NANC) signaling in the autonomic nervous system?

    <p>Substance P</p> Signup and view all the answers

    Acetylcholine is synthesized from which two main components?

    <p>Choline and acetyl-CoA</p> Signup and view all the answers

    What step in neurotransmission refers to the process of neurotransmitter release from vesicles into the synapse?

    <p>Exocytosis</p> Signup and view all the answers

    Which of the following NANC neurotransmitters is known for playing a role in vasodilation?

    <p>Nitric oxide</p> Signup and view all the answers

    Which step in neurotransmission would a drug most likely target to inhibit the release of neurotransmitters?

    <p>Release</p> Signup and view all the answers

    Which mechanism inhibits the breakdown of norepinephrine (NE)?

    <p>Inhibition of MAO</p> Signup and view all the answers

    Which classes of drugs can prevent the re-uptake of norepinephrine back into presynaptic neurons?

    <p>Tricyclic antidepressants and cocaine</p> Signup and view all the answers

    What best describes a common non-adrenergic, non-cholinergic (NANC) neurotransmitter's role in the autonomic nervous system?

    <p>Contributing to both excitatory and inhibitory responses</p> Signup and view all the answers

    Which of the following statements about COMT inhibitors is correct?

    <p>They inhibit the action of catechol-O-methyltransferase.</p> Signup and view all the answers

    What is the primary action of tricyclic antidepressants in relation to norepinephrine?

    <p>They inhibit its re-uptake into presynaptic neurons.</p> Signup and view all the answers

    Which of the following neurotransmitters is classified as a non-adrenergic non-cholinergic mediator in the parasympathetic nervous system?

    <p>Vasoactive Intestinal Peptide (VIP)</p> Signup and view all the answers

    What is the primary effect of hemicholinium on cholinergic neurotransmission?

    <p>Blocks the choline transporter</p> Signup and view all the answers

    Which drug is responsible for blocking the vesicle-associated transporter that affects cholinergic neurotransmission?

    <p>Vesamicol</p> Signup and view all the answers

    Which of the following is NOT a step where drugs can interfere with neurotransmission?

    <p>Modification of genetic material</p> Signup and view all the answers

    Which of the following neurotransmitters is specifically mentioned as a co-transmitter in the peripheral nervous system?

    <p>Adenosine triphosphate (ATP)</p> Signup and view all the answers

    Which neurotransmitter functions primarily in the sympathetic nervous system as a NANC mediator?

    <p>Nitric Oxide</p> Signup and view all the answers

    What is the function of monoamine oxidase (MAO) in neurotransmitter action?

    <p>Termination of neurotransmitter action</p> Signup and view all the answers

    Which of the following is a characteristic of non-adrenergic non-cholinergic (NANC) neurotransmitters?

    <p>They include mediators like serotonin and GABA</p> Signup and view all the answers

    What is the rate-limiting step in the synthesis of catecholamines?

    <p>Conversion of Tyrosine to Dopa</p> Signup and view all the answers

    Which enzyme is responsible for the conversion of Dopa to Dopamine?

    <p>Dopa decarboxylase</p> Signup and view all the answers

    Which statement about the metabolism of catecholamines is correct?

    <p>The oxidative branch of metabolism predominates, yielding vanillylmandelic acid (VMA).</p> Signup and view all the answers

    Which metabolite is produced in larger quantities from the oxidative branch of noradrenaline metabolism?

    <p>Vanillylmandelic acid (VMA)</p> Signup and view all the answers

    Which enzyme is NOT involved in the metabolism of catecholamines?

    <p>Aldose reductase (AR)</p> Signup and view all the answers

    Which substance can inhibit the rate-limiting step in catecholamine synthesis?

    <p>Metyrosine (α-methyltyrosine)</p> Signup and view all the answers

    What does MHPG sulfate excretion reflect?

    <p>Noradrenaline release in the brain</p> Signup and view all the answers

    Which catecholamine is formed after the enzymatic conversion of noradrenaline?

    <p>Adrenaline</p> Signup and view all the answers

    What is the role of the vesicular monoamine transporter (VMAT) in the transmission of adrenergic signals?

    <p>To store Noradrenaline (NA) in the vesicle for release</p> Signup and view all the answers

    Which enzyme is directly involved in the conversion of Dopamine to Noradrenaline (NA)?

    <p>Dopamine-β-hydroxylase</p> Signup and view all the answers

    Which transport mechanism employs a Na⁺ dependent carrier during adrenergic transmission?

    <p>Transport of Tyrosine into the presynaptic nerve terminal</p> Signup and view all the answers

    What is the role of choline acetyltransferase (ChAT) in cholinergic transmission?

    <p>It catalyzes the synthesis of acetylcholine.</p> Signup and view all the answers

    In cholinergic transmission, what triggers the release of acetylcholine (ACh) into the synapse?

    <p>Influx of Ca²⁺ ions</p> Signup and view all the answers

    Which of the following components is essential for synthesizing acetylcholine in nerve terminals?

    <p>Acetyl-CoA</p> Signup and view all the answers

    What is produced when Dopa is converted in the process preceding the formation of Noradrenaline?

    <p>Dopamine</p> Signup and view all the answers

    How is neurotransmitter action primarily terminated in the synapse?

    <p>By enzyme degradation or reuptake</p> Signup and view all the answers

    Which of the following neurotransmitters is classified under non-adrenergic, non-cholinergic (NANC) signaling?

    <p>Substance P</p> Signup and view all the answers

    What is the synthesis process of most neurotransmitters in the peripheral nervous system?

    <p>Synthesis occurs in nerve terminals from precursor molecules.</p> Signup and view all the answers

    Which component is directly involved in neurotransmitter release in response to nerve stimulation?

    <p>Calcium channels</p> Signup and view all the answers

    Which statement best reflects the primary mechanism through which drugs exert their effects on neurotransmission?

    <p>By interfering with specific steps in neurotransmitter synthesis, storage, release, or reuptake.</p> Signup and view all the answers

    Which of the following is the correct sequence of neurotransmitter action from synthesis to termination?

    <p>Synthesis → Storage → Release → Termination</p> Signup and view all the answers

    Which mechanism specifically inhibits the re-uptake of norepinephrine into the presynaptic neuron?

    <p>Tricyclic antidepressants</p> Signup and view all the answers

    What is the primary function of COMT inhibitors in the context of neurotransmitter activity?

    <p>Inhibit breakdown of norepinephrine</p> Signup and view all the answers

    Which of the following substances is classified as a non-adrenergic, non-cholinergic (NANC) neurotransmitter?

    <p>Substance P</p> Signup and view all the answers

    Which neurotransmitter's action is most likely affected by the use of MAO inhibitors?

    <p>Norepinephrine</p> Signup and view all the answers

    Which step in neurotransmission would MOST likely be influenced by the use of cocaine?

    <p>Re-uptake of neurotransmitters</p> Signup and view all the answers

    Which catecholamine is synthesized immediately after dopamine?

    <p>Noradrenaline</p> Signup and view all the answers

    What is the main urinary metabolite produced from the oxidative metabolism of noradrenaline?

    <p>Vanillylmandelic acid (VMA)</p> Signup and view all the answers

    Which enzyme is responsible for the production of adrenaline from noradrenaline?

    <p>Phenylethanolamine-N-methyltransferase</p> Signup and view all the answers

    What effect does metyrosine (α-methyltyrosine) have in the synthesis of catecholamines?

    <p>Inhibits the conversion of Tyrosine to Dopa</p> Signup and view all the answers

    Which of the following enzymes primarily contributes to the metabolism of catecholamines through oxidative reactions?

    <p>Aldehyde dehydrogenase (ADH)</p> Signup and view all the answers

    Which metabolite is associated with the reductive metabolism of noradrenaline?

    <p>3-methoxy-4-hydroxyphenylglycol (MHPG)</p> Signup and view all the answers

    What overall effect would increased levels of monoamine oxidase (MAO) have on catecholamines?

    <p>Decrease the levels of catecholamines in the body</p> Signup and view all the answers

    Which metabolite's excretion reflects the release of noradrenaline in the brain?

    <p>3-methoxy-4-hydroxyphenylglycol (MHPG)</p> Signup and view all the answers

    Which neurotransmitter is primarily categorized as a NANC mediator in the sympathetic nervous system?

    <p>Neuropeptide Y</p> Signup and view all the answers

    What mechanism is primarily targeted when a drug blocks the choline transporter in cholinergic neurotransmission?

    <p>Synthesis of acetylcholine</p> Signup and view all the answers

    Which of the following is NOT considered a major NANC mediator in the autonomic nervous system?

    <p>Acetylcholine</p> Signup and view all the answers

    What effect does vesamicol have on cholinergic neurotransmission?

    <p>Inhibits the storage of acetylcholine in vesicles</p> Signup and view all the answers

    Which of the following neurotransmitters is involved in vasodilation as a NANC mediator?

    <p>Nitric oxide</p> Signup and view all the answers

    Which step in neurotransmission is directly affected by monoamine oxidase (MAO)?

    <p>Termination of neurotransmitter action</p> Signup and view all the answers

    Which of the following substances can be considered a co-transmitter in the peripheral nervous system?

    <p>All of the above</p> Signup and view all the answers

    In what way can drugs interfere with the storage of neurotransmitters?

    <p>By inhibiting the transporter for moving neurotransmitters into vesicles</p> Signup and view all the answers

    What enzyme is responsible for converting Dopamine to Noradrenaline (NA) inside the vesicle?

    <p>Dopamine-β-hydroxylase</p> Signup and view all the answers

    Which component is essential for the transport of Tyrosine into the presynaptic nerve terminal?

    <p>Na⁺ dependent carrier</p> Signup and view all the answers

    What function does the vesicular monoamine transporter (VMAT) serve in adrenergic transmission?

    <p>Transports Dopamine into the vesicle</p> Signup and view all the answers

    Which two components are produced sequentially during the conversion process of Tyrosine?

    <p>Dopamine and Dopa</p> Signup and view all the answers

    Which of the following steps is directly influenced by an influx of Ca²⁺ at the nerve terminal?

    <p>Exocytosis of vesicles containing neurotransmitters</p> Signup and view all the answers

    What is the main precursor for the synthesis of acetylcholine (ACh) in the nerve terminal?

    <p>Choline</p> Signup and view all the answers

    Which statement best describes the process of neurotransmitter release in the autonomic nervous system?

    <p>Neurotransmitters are stored in vesicles and released upon nerve stimulation.</p> Signup and view all the answers

    What mechanism primarily terminates the action of neurotransmitters in the synapse?

    <p>Enzymatic breakdown and neuronal reuptake</p> Signup and view all the answers

    Which neurotransmitter is synthesized from acetyl-CoA and choline in cholinergic transmission?

    <p>Acetylcholine</p> Signup and view all the answers

    Which NANC neurotransmitter is known for its role in vasodilation?

    <p>Nitric oxide</p> Signup and view all the answers

    What is the function of the choline acetyltransferase (ChAT) enzyme in cholinergic transmission?

    <p>Converting acetyl-CoA into ACh</p> Signup and view all the answers

    What is the role of neuronal reuptake in neurotransmission?

    <p>To terminate the action of neurotransmitters in the synapse</p> Signup and view all the answers

    Which drug class is primarily used to inhibit the re-uptake of norepinephrine back into the presynaptic neuron?

    <p>Tricyclic antidepressants</p> Signup and view all the answers

    Which describes the storage of neurotransmitters within nerve terminals?

    <p>Stored in membrane-bound vesicles</p> Signup and view all the answers

    What role do COMT inhibitors play in neurotransmitter activity?

    <p>They inhibit the breakdown of norepinephrine.</p> Signup and view all the answers

    Which mechanism is involved in terminating the action of norepinephrine in the synaptic cleft?

    <p>Re-uptake into presynaptic neurons</p> Signup and view all the answers

    Which of the following best describes the role of MAO inhibitors in neurotransmission?

    <p>They inhibit the degradation of norepinephrine.</p> Signup and view all the answers

    What is the primary effect of using cocaine in the context of norepinephrine?

    <p>It inhibits the re-uptake of norepinephrine.</p> Signup and view all the answers

    Which neurotransmitter is primarily associated with vasodilation in the parasympathetic nervous system?

    <p>Nitric oxide</p> Signup and view all the answers

    What step of neurotransmission would be primarily affected by drugs that block vesicle-associated transporters (VAT)?

    <p>Storage of neurotransmitters in vesicles</p> Signup and view all the answers

    Which neurotransmitter acts as a co-transmitter in the sympathetic nervous system?

    <p>Neuropeptide Y</p> Signup and view all the answers

    Which drug specifically blocks the choline transporter, affecting acetylcholine synthesis?

    <p>Hemicholinium</p> Signup and view all the answers

    How do nitrogen oxide neurons primarily differ from cholinergic neurons in their signaling?

    <p>Nitric oxide is released into the bloodstream for systemic effects</p> Signup and view all the answers

    Which of the following mediators would most likely be categorized as a non-adrenergic, non-cholinergic (NANC) neurotransmitter involved in mood regulation?

    <p>Serotonin</p> Signup and view all the answers

    Which process involves the dissolution of neurotransmitters in the synapse, leading to their eventual breakdown?

    <p>Termination of action</p> Signup and view all the answers

    What is the major effect of monoamine oxidase (MAO) in the context of neurotransmitter action?

    <p>Degrading neurotransmitters in the synapse</p> Signup and view all the answers

    What is the function of the enzyme catechol-O-methyltransferase (COMT) in the metabolism of catecholamines?

    <p>It degrades catecholamines by methylation.</p> Signup and view all the answers

    Which of the following statements correctly describes the metabolic pathway of noradrenaline?

    <p>The oxidative branch mainly results in the formation of VMA as a metabolite.</p> Signup and view all the answers

    Which enzyme is involved in the conversion of Dopa to Dopamine?

    <p>Dopa decarboxylase</p> Signup and view all the answers

    What effect does metyrosine have on catecholamine synthesis?

    <p>Inhibits the conversion of tyrosine to dopa.</p> Signup and view all the answers

    Which of the following metabolites indicates the release of noradrenaline from the brain?

    <p>3-methoxy-4-hydroxyphenylglycol (MHPG) sulfate</p> Signup and view all the answers

    Which step in catecholamine metabolism is catalyzed by monoamine oxidase (MAO)?

    <p>Oxidation of catecholamines to their corresponding aldehydes.</p> Signup and view all the answers

    Which metabolite is primarily produced by the reductive branch of noradrenaline metabolism?

    <p>3-methoxy-4-hydroxyphenylglycol (MHPG)</p> Signup and view all the answers

    What is the outcome of the activity of phenylethanolamine-N-methyltransferase in catecholamine synthesis?

    <p>It catalyzes the methylation of noradrenaline to form adrenaline.</p> Signup and view all the answers

    Study Notes

    Neurotransmission in the Autonomic Nervous System (ANS)

    • The ANS is responsible for regulating involuntary bodily functions, including heart rate, digestion, and breathing.
    • Neurotransmission in the ANS involves the synthesis, storage, release, and termination of neurotransmitters.
    • Most neurotransmitters are synthesized in nerve terminals, stored in membrane-bound vesicles, and released into the synapse in response to nerve stimulation.
    • Neurotransmitter action is terminated by metabolism or neuronal reuptake.

    Cholinergic Transmission

    • Acetylcholine (ACh) is the primary neurotransmitter in the parasympathetic nervous system.
    • Choline, the precursor for ACh, is transported into the nerve terminal by the choline transporter (CHT).
    • ACh is synthesized from acetyl-CoA and choline by the enzyme choline acetyltransferase (ChAT).
    • ACh is transported from the cytoplasm into vesicles by a vesicle-associated transporter (VAT).
    • Action potentials cause an influx of Ca²⁺ through voltage-gated Ca²⁺ channels, leading to exocytosis of vesicles and release of ACh into the synapse.

    Adrenergic Transmission

    • Norepinephrine (NA) is the primary neurotransmitter in the sympathetic nervous system.
    • Tyrosine is transported into the presynaptic nerve terminal by a Na⁺ dependent carrier.
    • Tyrosine is converted to Dopa by the enzyme tyrosine hydroxylase.
    • Dopa is converted to Dopamine by the enzyme dopa decarboxylase.
    • Dopamine is transported into the vesicle by the vesicular monoamine transporter (VMAT).
    • Inside the vesicle, Dopamine is converted to Noradrenaline (NA) by the enzyme dopamine-β-hydroxylase.

    Non-Adrenergic Non-Cholinergic (NANC) Mediators

    • NANCs include neurotransmitters other than NA and ACh.
    • Major NANC mediators in the ANS include:
      • Nitric oxide and vasoactive intestinal peptide (VIP) in the parasympathetic NS.
      • ATP and neuropeptide Y in the sympathetic NS.
      • Others, such as 5-hydroxytryptamine (serotonin), GABA, and dopamine.

    Effects of Drugs on Neurotransmission

    • Drugs can interfere with neurotransmission at various steps:
      • Synthesis of NT
      • Storage of NT in vesicles
      • Release of NT into the synapse
      • Interaction of the NT with post-synaptic receptors
      • Termination of NT action

    Drug Effects on Cholinergic Neurotransmission

    • Hemicholinium blocks the choline transporter, preventing ACh synthesis.
    • Vesamicol blocks the vesicle-associated transporter, preventing ACh from entering vesicles.

    Drug Effects on Adrenergic Neurotransmission

    • Metyrosine inhibits the rate-limiting step of catecholamine synthesis, preventing the conversion of tyrosine to Dopa.
    • Reserpine inhibits the vesicular monoamine transporter, blocking NA from accumulating in vesicles.
    • Guanethidine prevents the release of NA from the presynaptic neuron.
    • COMT-inhibitors (e.g.entacapone) or MAO inhibitors (e.g.selegeline) inhibit the breakdown of NA.
    • Tricyclic antidepressants and cocaine can inhibit the reuptake of NA back into the presynaptic neuron.

    Neurotransmission in the Autonomic Nervous System

    • Neurotransmitters are synthesized in nerve terminals and stored in membrane-bound vesicles.
    • Neurotransmitters are released into the synapse in response to nerve stimulation.
    • Termination of neurotransmitter action occurs through metabolism or neuronal reuptake.
    • Drugs can influence specific steps in neurotransmission.

    Cholinergic Transmission

    • Choline is transported into the nerve terminal using the choline transporter (CHT).
    • Acetylcholine (ACh) is synthesized from acetyl-CoA and choline via the enzyme, choline acetyltransferase(ChAT).
    • ACh is transported into vesicles using a vesicle-associated transporter (VAT).
    • Influx of Ca²⁺ through voltage-gated Ca²⁺ channels triggers exocytosis of ACh into the synapse.

    Adrenergic Transmission

    • Tyrosine is transported into the presynaptic nerve terminal using a Na⁺ dependent carrier.
    • Tyrosine is converted to Dopa by the enzyme tyrosine hydroxylase.
    • Dopa is converted to Dopamine by the enzyme dopa decarboxylase.
    • Dopamine is transported into vesicles via the vesicular monoamine transporter (VMAT).
    • Inside the vesicle, Dopamine is converted to Noradrenaline (NA) by the enzyme dopamine-β-hydroxylase.

    Synthesis of Catecholamines

    • Catecholamines are synthesized through a series of enzymatic steps starting with Tyrosine.
    • The rate-limiting step in catecholamine synthesis is the conversion of Tyrosine to Dopa, and can be inhibited by metyrosine (α-methyltyrosine).

    Metabolism of Catecholamines

    • Catecholamines are primarily metabolized by two enzymes: catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO).

    Non-Adrenergic Non-Cholinergic (NANC) Mediators

    • NANC neurotransmitters are those that are not noradrenaline (NA) or acetylcholine (ACh).
    • Major NANC mediators:
      • Nitric oxide and vasoactive intestinal peptide (VIP) in the parasympathetic nervous system (PNS).
      • ATP and neuropeptide Y in the sympathetic nervous system (SNS).
    • Other NANC's include:
      • 5-hydroxytryptamine (serotonin)
      • GABA
      • Dopamine.

    Drug Effects on Neurotransmission

    • Drugs can interfere with neurotransmission at various steps:
      • Synthesis of neurotransmitter
      • Storage of neurotransmitter in vesicles
      • Release of neurotransmitter into the synapse
      • Interaction of the neurotransmitter with post-synaptic receptors
      • Termination of neurotransmitter action

    Drug Effects on Cholinergic Neurotransmission

    • Hemicholinium blocks the choline transporter, preventing ACh synthesis.
    • Vesamicol blocks the vesicle-associated transporter (VAT), preventing ACh transport into vesicles.

    Drug Effects on Adrenergic Neurotransmission

    • Cocaine and tricyclic antidepressants inhibit the re-uptake of NA back into the presynaptic neuron.
    • COMT inhibitors (e.g., entacapone) or MAO inhibitors (e.g., selegeline) can inhibit NA breakdown.

    Neurotransmission in the Autonomic Nervous System

    • The autonomic nervous system uses neurotransmitters to communicate between neurons.
    • Neurotransmitters are synthesized in nerve terminals, stored in vesicles, released into the synapse, and then removed from the synapse.
    • Drugs can affect each step in neurotransmission.

    Cholinergic Transmission

    • Choline: Precursor for acetylcholine (ACh) transported into the nerve terminal by the choline transporter (CHT).
    • Acetylcholine: Synthesized from acetyl-CoA and choline by the enzyme choline acetyltransferase (ChAT).
    • Vesicle-Associated Transporter (VAT): Transports ACh from the cytoplasm into vesicles.
    • Nerve stimulation triggers calcium influx, leading to exocytosis of vesicles and ACh release into the synapse.

    Adrenergic Transmission

    • Tyrosine: Transported into the nerve terminal by a sodium-dependent carrier.
    • Tyrosine Hydroxylase: Converts tyrosine to dopa.
    • Dopa Decarboxylase: Converts dopa to dopamine.
    • Vesicular Monoamine Transporter (VMAT): Transports dopamine into the vesicle.
    • Dopamine β-Hydroxylase: Converts dopamine to noradrenaline (NA) within the vesicle.

    Catecholamine Synthesis

    • Tyrosine is the precursor for catecholamines.
    • The rate-limiting step in catecholamine synthesis is the conversion of tyrosine to dopa, which can be inhibited by metyrosine.
    • Catecholamines: Dopamine, noradrenaline, adrenaline

    Catecholamine Metabolism

    • Catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) are the main enzymes that metabolize catecholamines.
    • The primary urinary metabolite of noradrenaline is vanillylmandelic acid (VMA).

    Non-Adrenergic Non-Cholinergic (NANC) Mediators:

    • NANC neurotransmitters are those other than noradrenaline and acetylcholine.
    • NANC mediators in the peripheral nervous system include:
      • Parasympathetic: Nitric oxide, vasoactive intestinal peptide (VIP)
      • Sympathetic: ATP, neuropeptide Y
      • Others: 5-hydroxytryptamine (serotonin), GABA, dopamine

    Effects of Drugs on Neurotransmission

    • Drugs can interfere with neurotransmission by affecting:
      • Neurotransmitter synthesis
      • Storage of neurotransmitters in vesicles
      • Release of neurotransmitters into the synapse
      • Interaction of neurotransmitters with post-synaptic receptors
      • Termination of neurotransmitter action

    Drug Effects on Cholinergic Neurotransmission

    • Hemicholinium: Inhibits choline transport, preventing ACh synthesis.
    • Vesamicol: Blocks the VAT, preventing ACh transport into vesicles.

    Drug Effects on Adrenergic Neurotransmission

    • α-Methyltyrosine (Metyrosine): Inhibits tyrosine hydroxylase, reducing catecholamine synthesis.
    • Reserpine: Depletes noradrenaline stores in vesicles.
    • Guanethidine: Displaces noradrenaline from vesicles and inhibits release.
    • COMT Inhibitors: Inhibit the breakdown of noradrenaline, prolonging its action.
    • MAO Inhibitors: Inhibit the breakdown of noradrenaline, prolonging its action.
    • Tricyclic Antidepressants, Cocaine: Inhibit the re-uptake of noradrenaline into the presynaptic neuron, prolonging its action.

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