PSYA01H3 Lecture Notes - Lecture 24: Anandamide, Striatum, Endocannabinoid System

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Published on 7 Dec 2015
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PSYA01Lecture#24CannabisandTheBrain:ADevelopingStory
Background
● Cannabis(marijuana)mostwidelyusedillicitdrug
● Ratesof‘everuse’inNorthAmericaover15yrsold:40%
● RatesofCannabisDependence:9%ingeneralpopulation;21%inyouth(under20)
● SlightlyhigherinM:F
● Median/meanageoffirstuse~15years
Adolescence
● Profoundneurochemicalchangesoccurfrompubertytoadulthood
● Hormonesmodulateneurotransmission,includingbrainrewardfunction
● Sometransmittersundergopruning(dopamine)othersstable(serotonin)Dopamin,
Serotoninhigherinadolescence
● Delicatebalancebetweenneurotransmittersystemswithcomplexfeedbackcircuitry
(interactive“pathways”)
● “Ubiquitous”neurotransmittersGABAandglutamatesettheoverallscoreonneural
activityviainhibitionandexcitation,respectively
● Especiallyabundantinprefrontalcortex(PFC)
● Ageofonsetamongthestrongestpredictorsofeventualsubstancedependance;same
istrueformarijuana
EndocannabinoidSystem
● Diffusedistributionthroughoutbodyandbrain
● Modulatesallofthefunctionsdescribedaboveaswellaspain,immunefunction
● InfluencesbalanceofinhibitionexcitationviaactionsonGABAglutamate
● Twomainreceptors:CBI(mainlyinbrain),CB2(mainlyinperiphery)
● Anandamide(Sanskrit“bliss”)endogenouscannabinoidtransmitter
ExogenousCannabinoid:Marijuana
● Containsmorethan80differentcannabinoids
● Twokeyconstituents:Δ9Tetrahydrocannabinol(THC);cannabidiol(CBD)
● THCpsychoactiveproperties(‘bad’)
● CBDpain,antiseizure,antioxidanteffects(‘good’)
● BalanceofTHC:CBDcriticaltorisk:benefitprofileofdifferentstrainsofmarijuana
MarijuanaandAdolescentBrain
● PruningimbalanceofGo(Dopamine,Glutamate)andNoGo(Serotonin,GABA)
circuitryinadolescence
● ImbalanceofTopDown(PFC>striatum)vs.Bottomup(striatum>PFC)influence
● Increasedsusceptibilitytosensitization(proliferationofdendritespines:glutamate
dopamine)
● THCinhibitsGABA;maydisinhibitsensitizationrelatedprocesses
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