Year of Publication

2011

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Pharmacy

Department

Pharmaceutical Sciences

First Advisor

Dr. Linda P. Dwoskin

Abstract

This dissertation work investigated the effect of acute and repeated in vivo administration of lobeline on dopamine transporter (DAT) and vesicular monoamine transporter (VMAT2) function. The effects of lobeline were then compared to the effects of acute and repeated in vivo administration of methylphenidate and amphetamine to determine if lobeline produced similar effects compared to these Attention Deficit Hyperactivity Disorder (ADHD) medications. These medications are considered the first line of pharmacotherapy for ADHD, although there is a growing concern associated with their potential for abuse and other side effects. This merits the need for novel ADHD treatments that have a safer side effect profile. If lobeline alters DAT and VMAT2 function in the same way as methylphenidate or amphetamine, further investigation may be necessary to evaluate lobeline as a potential treatment for ADHD. Kinetic analysis of [3H]dopamine (DA) was utilized to determine the effect on DAT and VMAT2 function in rat striatum. Results from the DAT experiments, revealed that lobeline as well as amphetamine had no effect on DAT function. However, methylphenidate increased DAT function after acute and 7-day treatment. None of the drug treatment regimens altered Km. To determine if the methylphenidateinduced increase in DAT function was due to DAT trafficking, biotinylation and Western blot analyses were performed. Acute administration of methylphenidate did not alter surface DAT, however repeated administration of methylphenidate for 7 days decreased intracellular DAT, suggesting that methylphenidate redistributes DAT in a time-dependent manner. Similar results were found in the VMAT2 experiments. Lobeline and amphetamine had no effect on VMAT2 function after acute or repeated administration. Amphetamine decreased the Km after repeated administration for 7 days. Methylphenidate increased VMAT2 function after acute and repeated administration for 7 days. The overall results of these experiments suggest that methylphenidate interacts with DAT and VMAT2 in a different manner than amphetamine and lobeline. In addition, since lobeline and amphetamine had no effect on DAT and VMAT2 function, further investigation is warranted to elucidate the underlying mechanisms of the therapeutic actions of these agents. This additional information will aid in the development of novel treatments for ADHD.

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