Drugs and Hormones

Drugs and Hormones - DrugsofAbuse Whatisadrug?

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Drugs of Abuse
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What is a drug? Any biological substance that alters or  affects some bodily functions Psychoactive drugs:   chemical substances that  Psychopharmacology: studies how drugs alter the NS and behavior
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Common Properties Tolerance -  dec.  responsiveness  to a drug User has to take    amts of drug  to feel the same  effects Small Large Drug dose Little effect Big effect Drug effect Response to first exposure After repeated exposure, more drug is needed to produce same effect
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Common Properties Withdrawal -  unpleasant physical rxn to lack  of drug Causes a variety of  symptoms: Sweating Shaking Nausea/ vomiting Sleeplessness Loss of appetite
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Common Properties Physical dependence-  body/brain  chemistry are adapted to drug Cannot function w/out its presence Psychological dependence-  people  believe they need the drug to respond to  stresses of daily living  
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Neural basis of drug activity Mesolimbic DA Pathway Located in ventral  tegmental area (VTA) and  projects to basal ganglia,  and to limbic system via  the NAc, and to medial  prefrontal cortex.  Involved in modulating  behavioral responses to  stimuli that activate feelings  of reward (motivation) and  reinforcement through DA.
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Mesolimbic Dopamine Pathway Pathway triggered during drug intake and  drug-seeking behavior (Phillips et al.,  2003) Same pathway is used during natural  rewards (i.e. food, sex)
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Blood-brain barrier Prevents substances (including drugs)  from entering CNS via bloodstream Small molecules (i.e. oxygen, carbon dioxide)  are fat soluble and can freely cross the BBB.  Large, charged molecules ( glucose, fats,  amino acids) must be actively transported  across the BBB Endothelial cells and astrocytes keep  drugs out of brain Some areas of the brain are barrier free
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Barrier-free brain sites
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Routes of drug administration Oral: safest, easiest, and most common  route Inhalation Injection Transdermal  The more barriers the drugs have to go  through, the more drug needed to have a  desired effect
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Inhalation Advantage: Fastest  method, 7-10  seconds for the drug  to reach the brain Disadvantages- Most  addictive route b/c of  speed of entry  Difficulties in  regulating the exact  amount of dosage 
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Injection I ntravenous- into a vein Intramuscular- into a muscle Advantages - 15-30 sec for 
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Drugs and Hormones - DrugsofAbuse Whatisadrug?

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