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NEUR 2200
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PSYCHOPHARMACOLOGY study of how drugs affect the nervous systemDrugs are grouped by there behavioural effects1Principles of Psychopharmacology Drugs are chemicals used to bring about a change in the body They are used to diagnose treat and prevent illnesses PSYCHOACTIVE DRUGS substance that alter mood thought and behaviourand are used to manage neuropsychological disorders Many of these drugs are taken for nonmedicinal purpose and are abused These drugs impair users functioning promotes craving and may produce addictionaDrug routes the way which a drug enters the body is called route of administration These routes can beiOrally easy and convenient But not all drugs can pass through the barriers of digestive tracts walliiInhalation administered as gases or aerosol which will go through the cell linings of the respiratory tract easily and are absorbed through the membranes into the bloodstream as quickly as they are inhaled Such drugs are nicotine marijuana cocaineiiiour skin being the largest organ in the body has 3 layers of cells to be a protective body coat Some small molecule ie nicotine penetrate the skins barrier as easy as the cell lining of respiratory tract whereas large molecules ie steroids cannotivBloodstream fastes route and few obstaclesvDirect injection to the brain has even fewer obstaclesviFigure 81bAbsorption is affected by physical and chemical properties of drugiweak acid such as alcohol is easily absorbed through the stomach liningiiweak base such as Phenobarbital which is an anaesthetic cannot pass through the stomach lining and thus has to pass in the intestines instead note this process may destroy a weak baseiiiafter absorption by the stomach or intestine the drug enters the bloodstream Drug must be hydrophilic to be carried in the bloodstream because blood has high concentration of waterthe drug is diluted by the bodies 6L of water NO HYDROPHOBIC SUBSTANCE ENTER BLOODivNext drugs goes into the extracellular which requires the molecules to be small to pass through pores of the capillaries Then it is diluted further by the bodies 35L of extracellular content of watervWith each opbstacle encountered during its route to the brain drug dosage can be reduced by 10x ie amphetamine needs 1000 microgram if taken orally to show effect If inhaled you need only 100 micrograms for same effect and only 10 microgram if injectedcBlood Brain Barrier abbreviated BBB the tight junction between the cells of the blood vessels in the brain that prevent passage of most substances iBrain capillaries are composed of single layer endothelial cells These cells are tighltly fused to form a tight junction So most molecules cannot passsqueeze between them iiThe figure above also shows the glial cells surrounding the blood cappuilary wall forming 80 percent of it The glial cells provide route for exchange of foodwastes between capillaries and the brains extracellular fluid They may also play a role in maintaining the tight junction between the endothileal cells and dilate the capillaries to increase blood flow to areas in need iiiTHREE REGIONS IN BRAIN THAT LACK BBB1PITUATARY GLAND source of hormone that are secreted into the blood stream and the release iis triggered by other hormones carried to the pituitary by the blood 2AREA POSTERMA entry of toxic substances that induce vomiting3PINEAL GLAND entry of chemicals that affect the danight cyclesivTo carry its work the brain needs oxugen and glucose for fuekl and amino acid building They must reach the brain cells from the blood Two ways this is achieve1small molecules that arent ionized like oxygen or carbon dioxide and are fat soluble can pass easily through the endothileal membrain2 molecules of glucose amino acids and other food components use ACTIVE TRANSPORT SYSTEM OR PUMPSproteins specialized for transport of particular substancevOne its passed through BBB it is easily moved to the neurons and gliaviA drug can reach the brain only if th emocleculas are small and not ionized or if the drug has a chemical structure trhat allows it to be carried across the membrane by an active transport system
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