Undergraduate Honors Theses

Thesis Defended

Spring 2016

Document Type


Type of Thesis

Departmental Honors


Psychology & Neuroscience

First Advisor

Dr. Ryan Bachtell

Second Advisor

Dr. Heidi Day

Third Advisor

Dr. Christopher Lowry


Caffeine is a frequently used psychoactive substance and consumption by children and adolescents continues to rise. Here, we examine the effects of withdrawal from chronic adolescent caffeine consumption on anxiety-related behaviors and the serotonin system, specifically the dorsal raphe nucleus. Adolescent male rats consumed caffeine (0.3 g/L) for 28 days from postnatal day 28 (P28) to P55 and control rats consumed water. Behavioral testing for anxiety-related behavior began in adulthood (P62) 24 hours after removal of caffeine. Adolescent caffeine consumption augmented anxiety-related behavior in the elevated plus maze and social interaction tests. Gene expression of tryptophan hydroxylase 2 (tph2), the rate-limiting enzyme involved in serotonin synthesis, and solute carrier family 6 neurotransmitter transporter member 4 (slc6A4), the gene encoding the serotonin transporter, were used as markers of serotonin transmission and their expression was evaluated in different subregions of the raphe. Expression of tph2, but not slc6A4, was decreased in all dorsal raphe subregions following withdrawal from adolescent caffeine consumption. Caffeine challenge decreased tph2 expression in vehicle-treated rats in the DRD and slc6a4 expression in caffeine-treated rats in the DRI. Together, these findings suggest that adolescent caffeine consumption and withdrawal may alter some aspects of the serotonin system, although their functional relationship to the emergence of withdrawal-induced anxiety is not clear.