recreational drugs

• Cocaine

  stimulant effect on CNS especially on neurons of brains reward system (mesocorticolimbic pathway).

  Blocks reuptake of dopamine by binding to dopamine transporter molecules on terminal buttons on presynaptic neuron so they all bind to receptors on postsynaptic neuron - dopamine rush - euphoric high.

  Eventual tolerance develops and higher doses seeks - addicton, withdrawal
• Heroin

  Depressant effect on CNS - including activity of neurons involved in pain - mostly processed into closely related opioid morphine which then binds with a specific opioid receptor at the synapse found in the cerebral cortex, limbic system and hypothalamus (taps into opined system)

  Opioid system = natural painkillers - produce endorphins etc - this response is enhanced

  Eventual down regulation and desensitise to effect of drugs
• cocaine strength

  Weinshenker got rats to choose between pressing buttons for food or for 'pleasure shock' (cocaine) - they chose shock

  Their mesocorticolimbic pathway was then removed and they chose food

  This shows how it significantly affects the reward system and supports effect of cocaine on dopamine
• cocaine weakness

  Using animals to understand humans may not be accurate as we all evolved differently, share a genotype not a phenotype. Human brain is more complex, we have a bigger cerebral cortex than rats and therefore more advanced cognitive processing

  Can't generalise findings to humans
• heroin strength

  Can be used as application to develop treatment for addicts - once heroin found to be an agonist drug, other drugs developed with a reverse mode of action. Naloxone is an antagonist drug - blocks opioid receptors from binding to morphine + doesn't produce euphoria so can help manage withdrawal process
• heroin weakness

  Addicts will still struggle with withdrawal symptoms after naloxone and highly complex interaction of neurotransmission systems affected by drugs is not fully understood