Samenvatting

Serotonin, or 5-hydroxytryptamine (5-HT), is a molecule which is widely found in the natural world. It is found in both plants and animals. In animals its main use is that of neurotransmitter. Selective serotonin reuptake inhibitors (SSRIs) are a class of antidepressants aimed at increasing the extracellular levels of serotonin through inhibition of 5-HT reuptake and thereby enhancing the 5-HT signal. Reuptake of extracellular 5- HT is achieved through the 5-HT transporter (5-HTT). In contrast with the effects of SSRIs, lowered 5-HTT expression is associated a vulnerability to depression. Both 5-HTT knockout mice and rats display increased depression related behaviours. The dorsal raphe nucleus (DRN) and the medial prefrontal cortex (mPFC) together may play a role in this increased vulnerability to depression.
Homozygous (-/-) and heterozygous (+/-) 5-HTT knockout rats were compared with wild type (WT, +/+) rats. Electrophysiological measurements were performed in a number of situations. Extracellular single unit and EEG recordings were made in the home cage, during mild stress and open field paradigms as well as during light induced restfulness. The number of central area crossings in the open field was assessed. These experiments were performed by researchers blind to the genotype.
Genotype information of the animals has not yet been revealed. However, results indicated two of the genotypes crossed the border of the open field’s central area more than the remaining genotype. Most likely this means that +/+ and +/- animals respond similarly to the open field. Cells were found that seemed to be related to mobility. Sleep patterns in EEG and firing rate were found during a home cage recording. This might serve as a way to confirm putative sleep patterns.
Much of the wealth of data from the animals used has not yet been analysed. Further analysis should provide more insight into the 5-HTT KO rat.