HL 2 Biology

E.4c Neurotransmitters & Drugs

excitatory psychoactive drugs: nicotine, cocaine, amphetamines

inhibitatory psychoactive drugs: benzodiazepines, alcohol, tetrahydrocannabinol (THC)

<<Effects of THC and Cocaine at Synapses in the Brain>>

THC

  • inhibitory psychoactive drug
  • decreases synaptic transmission
    • cannabinoid synapses= post-synaptic neuronal release endo-cannabanoid neurotransmitters
      • endo-cannabanoids bind to cannabinoid receptors (at pre-synaptic neurons)
      • pre-synaptic neuronal release of neurotransmitters
    • binds to cannabinoid receptors
      • release neurotransmitters from the pre-synaptic neurons (e.g.GABA)
      • fall in GABA releases dopaminergic synapses from inhibition
      • increase in dopamine release in the pleasure pathway

cocaine

  • excitatory psychoactive drugs
  • increases synaptic transmission
  • triggers transmission at synapses in the brain (use dopamine as neurotransmitter)
    • binds to membrane proteins that pump dopamine back into the pre-synaptic neurons
    • build-up dopamine in synapse
  • excites dopaminergic synapses, produce euphoria (pleasure)
    • e.g. eating, sex
  • addictive
    • brain adapts to cocaine use by reducing dopamine receptors
    • stop in usage of cocaine often causes depression
  • crack: heated cocaine and inhaled as a vapor
    • rapidly absorbed;
      •  greater intensity of effects
      • greater addictive potential
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