
Cholecystokinin(CCK)isoneofthemostimportanthormoneregulatorsofthedigestiveprocess.Thepeptideisconcentratedintheproximalsmallintestine(CCKcells)andissecretedintothebloodinresponsetotheingestionofproteinsandfats,whereitsactionsincludethestimulationofpancreaticsecretion,themodulationofinsulinoutput,theregulationofgastricemptying,andgallbladdercontraction.InthecentralnervoussystemCCKergicfibresarewidespread,beingparticularlyabundantinthecerebralcortex.Insomemesolimbicneuronsprojectingtothenucleusaccumbens,CCKiscolocalisedwithdopamineandithasbeensuggestedthatCCKmightfacilitatethefunctionofdopamineineventssuchasstimulusrewardassociativebehaviour.SecretionofCCKfromthemurinetumourcelllineSTC1hasbeenshowntobestimulatedbypituitaryadenylatecyclaseactivatingprotein(PACAP)andhasraisedthepossibilitythatPACAPmayfunctionasaneuromodulatorofCCKreleasefromgutendocrinecellsinvivo.CCK-8isalsosuspectedtoheightenpainsensationindiabetics.
Image:Cholecystokinin8terminalsandfibersinratdorsalhorn(spinalcord),vibratomesections,ABCdetection.