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NEUR 2600 (19)

The Synapse

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University of Lethbridge
NEUR 2600
Ian Whishaw

Synapses - the site of drug action February-15-13 11:00 AM - Drugs can act as agonists, or antagonists (decreases) - 5 classes of drugs based on behavioural effects - There is no one-to-one action of a drug as most have effects at many different kinds of synapses and these diverse effects often account for the side effects of their actions. Administration/elimination - The route of administration 1. Injecting a drug directlyi nto the brain allow it to act quickly in low doses because there are no barrier. 2. Take drugs orally is the safest, easiest and more convenient way to administer them 3. Drugs that are weak acids pass from the stomach into the bloodstream 4. Drugs that are weak bases pass from the intestines to the bloodstream 5. Drugs injected into muscle encounter more barriers than do drugs inhaled 6. Drugs inhaled into the lungs encounter few barriers en route to the brain 7. Drugs injected into the bloodstream encounter the fewest barrier to the brain but must be hydrophilic 8. Drugs contained in adhesive patches are absorbed through the skin Trace amounts of common anti-anciesty drugs in rivers is altering the behaviors of unsuspecting fish Ecoestrogens - feminizing males Absence of lead in gas - reduced violent crime Amphetamine: route of administration determines dose required 1. Oral 1000 micograms 2. Intraveneous 100 3. CSF 10 4. Neuron 1 The Blood-Brain Barrier - The BBB tightly controls what is allowed into the brain and so resists many chemicals, drugs, etc How it Works - Capillaries in the brain are not leaky, have tight junction and are covered with astrocyte feet. These properties prevent materials from moving in and out easily -> Basis of BBB ○ Capillaries in the body are leaky and have few tight junctions. Materials can move in and out relatively easy - Small uncharged molecules are able to pass through - Certain other molecules are carried across the membrane by active transport - Large and electrically charged molecules are unable to pass out of the capillary 3 Locations at which there is no BBB - Pineal gland: allows entry of chemicals that affect day-night cycles - Pituitary: allows entry of chemicals that influence pituitary hormones - Postrema (area): allows entry of toxic substances that induce vomiting Drug Classification - The most useful classification system uses behavioral effects of drugs Agonist or Antagonist 1. Synthesis 2. Storage 3. Release - Some can block release 4. Receptor Interaction - Some can block the receptor 5. Inactivation - Acetylcholine gets torn apart into acetyl and choline, but some drugs block that 6. Reuptake - Some can block reuptake 7. Degradation Agonist (+) Antagonist (-) ACh - synapse (muscle-nicotinic) - Choline-rich diet increases available acetylcholine (ACh) Normal ○ Agonist: black widow spider venom promotes release of ACh ○ Antagonist: bolutin (food poisoning) toxin blocks release of ACh Relief from anxiety Disinhibition ○ Agonist: nicotine stimulates ACh receptors Sedation ○ Antagonist: curare (poisons animals) blocks ACh receptors Sleep ○ Agonist: Physostigmine and organophosphates block the inactivation of ACh
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