The 3′-UTR VNTR polymorphism has also been studied in relation to acute responses to methylphenidate in children that have been diagnosed with ADHD. In a pilot study, eight children received acute doses of methylphenidate before SPECT neuroimaging (Rohde et al. 2003). Children homozygous for the 10-repeat allele exhibited greater cerebral blood flow, which may reflect higher transporter activity, in the frontal and basal ganglia brain areas in response to methylphenidate than children who were not homozygous for the 10-repeat allele.
