 Previously it was thought that the elevated number of dopamine transporters in people with ADHD was part of the pathophysiology but it appears that the elevated numbers are due to adaptation to exposure to stimulants . Current models involve the mesocorticolimbic dopamine pathway and the locus coeruleus @-@ noradrenergic system . ADHD psychostimulants possess treatment efficacy because they increase neurotransmitter activity in these systems . There may additionally be abnormalities in serotoninergic and cholinergic pathways . Neurotransmission of glutamate , a cotransmitter with dopamine in the mesolimbic pathway , seems to be also involved . 
