For some behavior there are consistent differences between individuals within a population, which is called animal personality. Across species, ranging from insects to mammals, personality has been described along behavioral gradients like activity, exploration, boldness and aggression. Monoamines such as dopamine have been shown to be essential for modulating animal behavior and could therefore be important also in explaining variation in animal personality. Supporting this, the dopaminergic system affect activity (in Confused flour beetles), and aggression (in Mediterranean field crickets). However, the causality and effect of dopamine on these behaviors, and also other behavioral traits used to describe personality is currently less explored. This study experimentally investigated how increased level of dopamine affects activity, boldness, exploration and aggression in Mediterranean field crickets (Gryllus bimaculatus). I show that dopamine manipulation had no effects on measured behavior. These results indicate that increased dopamine levels do not affect the scored personality traits in Mediterranean field crickets. The causality and generality of the relationship between dopamine and behavior used to score variation in personality is thus not clear in this species.

Many human pharmaceuticals have limited biodegradability and can end up in the aquatic environment. The effects of these pharmaceuticals on aquatic organisms is not fully understood. Ropinirole is a drug used to treat Parkinson’s disease. Ropinirole is a dopamine agonist that targets the dopaminergic system that many diverse organisms share. In this study, threespined sticklebacks (Gasterosteus aculeatus) were used to investigate the effect of ropinirole on wild animals. Wild captured sticklebacks were exposed to ropinirole, ropinirole and fluoxetine, or untreated control. The fish were sacrificed at two different time points to study the effects on gene expression after long and short- time exposure of the drug. Gene expression of two dopamine receptor genes (drd2 and drd1b) and one adrenergic receptor gene (adrd2a) is studied in this project. The fish brains were dissected, total mRNA isolated and translated to cDNA, and finally qPCR was done. The expression of drd2 and adrd2a genes did not differ across the treatment groups or time. Drd1b showed higher expression at long term of exposure relative to short time exposure to ropinirole, but no other differences were observed between treatment groups. Collectively, my results show that ropinirole, or ropinirole together with fluoxetine did not interact with the adrenergic receptor or the dopamine 2-receptor. Exposure to ropinirole longer time can upregulate genes, as seem for the gene drd1b.  Overall, these results show that pharmaceuticals in the environment can affect gene expression on other animals than the targeted humans.