Synapses and drugs

• What are the 2 categories of drugs?

  Agonists and antagonists
• What do agonists do?

  • increases depolarisation of post-synaptic neurone
  • stimulants
  • more acetylcholine released
  • acetylcholine is not broken down
  • more Ca2+ channels open

  All of these mean more acetylcholine binds to receptor proteins, so more Na+ channels open
• What do antagonists do?

  • decreases depolarisation of post-synaptic neurone
  • sedatives
  • less acetylcholine released
  • blocks the binding site on the receptor protein, so acetylcholine can't bind
  • blocks Na+ / Ca2+ channels/reuptake proteins

  All of these mean less acetylcholine binding to receptor proteins, so fewer Na+ channels open
• What 2 things are organophosphates used for?

  Pesticides and nerve agents
• Which aspect of synaptic transmission do organophosphates affect?

  Breakdown of acetylcholine by acetylcholinesterase (they are a non-competitive inhibitor)
• What happens to acetylcholine as a result of using organophosphates?How does this affect the post-synaptic neurone?

  It does not get broken down and remains attached to the receptor proteins on the post-synaptic membrane

  Na+ channels are always open and always depolarised (agonists)