Neurotransmitters II

Question 1

describe quantal release of transmitters

Answer 1

• quantal size
  
  • post-synaptic response to the transmitter ejected from a single vesicle
• quantum content
  
  • number of vesicles released per impulse

Question 2

describe the mechanism of action of botulinum toxin

Answer 2

• enters terminals of peripheral motor neurons and cleaves synaptobrevin
  
  • disrupts docking and therefore ACh release
    
    • weakness results

Question 3

describe the mechanism of action of tetanus toxin

Answer 3

• bacterial protease arises from infxn
• enters terminals of peripheral motor neurons
  
  • undergoes retrograde transport
  • transferred to inhibitory interneuron
  • cleaves synaptobrevin
  • disrupts docking and therefore glycine release
    
    • motor neurons disinhibited
      
      • muscle spasms result

Question 4

describe the moa of aminoglycoside antibiotics

Answer 4

• block voltage-gated Ca channels
  
  • reduce impulse-dependent influx of Ca
    
    • release of ACh from peripheral motor neurons suppressed
      
      • weakness results

Question 5

describe the moa of 4-aminopyridine

Answer 5

• blocks voltage-gated potassium channels
  
  • increased duration of APs
    
    • increased influx of Ca through voltage-gated Ca channels
      
      • increased release of ACh by peripheral motor neurons
        
        • enhanced muscular contractions due to increased quantal content

Question 6

describe the acoustic startle response

Answer 6