Lecture 10 — Neurochemical Transmission and ANS Drugs
Condensed source-based study notes. Consult original slides for diagrams and finer details.
Core Neurotransmitters and Drug Classes
• Autonomic drugs mimic or block acetylcholine (ACh) and norepinephrine/epinephrine.
• Agonists activate receptors; antagonists prevent endogenous transmitters from activating them.
• Cholinergic/muscarinic agonists are parasympathomimetics; muscarinic antagonists are parasympatholytics.
• Adrenergic agonists are sympathomimetics; adrenergic antagonists are sympatholytics.
Steps in Neurochemical Transmission
• 1. Synthesis of transmitter. 2. Storage. 3. Action-potential-triggered release.
• 4. Interaction with effector-cell receptors and resulting response.
• 5. Rapid removal from the receptor vicinity. 6. Recovery of the effector cell.
Drug Actions at Different Steps
• Norepinephrine synthesis, storage, release and degradation are illustrated; MAO and COMT are named as degradation enzymes.
• Inhibition of transmitter degradation can increase transmitter accumulation.
• Local anesthetics, tetrodotoxin and saxitoxin are listed as inhibitors of action-potential propagation through sodium-channel blockade.
• Cocaine is described as blocking transmitter reuptake, increasing the transmitter effect at postsynaptic receptors.
• Direct cholinergic agonists act at ACh receptors; indirect cholinergic agonists increase ACh availability, including through acetylcholinesterase inhibition.
