Synapses, Drugs, & Addictions

• Drugs affecting synapses

  Can either block the effects (antagonist) or mimic/increase the effects (agonist) of a neurotransmitter
• Affinity


  How strongly the drug attaches to the receptor
• Neurotransmitters


  • Nitric Oxide
• Negative feedback from the postsynaptic cell

  Autoreceptors inhibit further synthesis and release of neurotransmitter
• A mixed agonist-antagonist drug acts as an agonist for some behavioral effects or doses and as an antagonist for others
• Cannabinoids


  • Active chemicals in marijuana that bind to anandamide or 2-AG receptors on presynaptic neurons
• Nicotine


  • Stimulates acetylcholine receptors, known as nicotinic receptors
• Reverse transmitters


  • Anandamide and 2-AG
• At a synapse, a neuron releases chemicals known as neurotransmitters that affect another neuron
• Ways drugs can influence synaptic activity

  1. Alter synthesis of neurotransmitter

  2. Disrupt vesicles

  3. Increase release

  4. Decrease reuptake

  5. Block breakdown into inactive chemicals

  6. Stimulate or block postsynaptic receptors
• Neuropeptides


  Often referred to as neuromodulators due to properties that set them apart from other transmitters
• Opiate drugs


  • Derived from, or chemically similar to, those derived from the opium poppy
• Efficacy


  The tendency of the drug to activate a receptor
• Activating receptors of the postsynaptic cell

  1. Ionotropic effects

  2. Metabotropic effects

  3. G protein

  4. Second messenger
• Inactivation and reuptake of neurotransmitters

  1. Acetylcholinesterase breaks the receptor into acetate and choline

  2. Reuptake occurs through transporters

  3. Catechol-O-methyltransferase (COMT) breaks down remaining transmitter molecules

  4. Methylphenidate (Ritalin) is a stimulant drug prescribed for attention deficit/hyperactivity disorder
• Hallucinogenic drugs

  • Lysergic acid diethylamide (LSD)