Comprehensive Investigation of Metabolic Changes Occurring in the Rat Brain Hippocampus after Fluoxetine Administration Using Two Complementary In Vivo Techniques: Solid Phase Microextraction and Microdialysis

Abstract

Fluoxetine is among the most prescribed antidepressant drugs worldwide. Nevertheless, limited information is known about its definitive mechanism. Although in vivo examinations performed directly in related brain structures can provide more realistic, and therefore more insightful, knowledge regarding the mechanisms and efficacy of this drug, only a few techniques are applicable for in vivo monitoring of metabolic alterations in the brain following an inducement. Among them, solid phase microextraction (SPME) and microdialysis (MD) have emerged as ideal in vivo tools for extraction of information from biosystems. In this investigation, we scrutinized the capabilities of SPME and MD to detect ongoing changes in the brain following acute fluoxetine administration. Sequential in vivo samples were collected simultaneously from male rats' hippocampi using SPME and MD before drug administration in order to establish a baseline; then samples were collected again following fluoxetine administration for an investigation of small molecule alterations. Our results indicate that MD provides more comprehensive information for polar compounds, while SPME provides superior information with respect to lipids and other medium level polar molecules. Interestingly, in the lipidomic investigation, all dysregulated features were found to be membrane lipids and associated compounds. Moreover, in the metabolomic investigations, dysregulation of hippocampal metabolite levels associated with fatty acid transportation and purine metabolisms were among the most notable findings. Overall, our evaluation of the obtained data corroborates that, when used in tandem, SPME and MD are capable of providing comprehensive information regarding the effect of fluoxetine in targeted brain structures and further elucidating this drug's mechanisms of action in the brain.

SPME Probes: A Novel Chemical Biopsy Tool for Spatially Resolved Profiling of Human Brain Tissue in vivo

“…Based on this nding, the lipidomic analysis was carried out using the C18 ber. This is consistent with the work of Boyaci et al 11 , who used the C18 sorbent for their lipidomics analysis, and a mixed-mode extractive phase for their metabolomics analysis.…”

“…SA1-SA4). Nonetheless, it is important to note that the range of extracted metabolites was still limited, and, consistent with the research conducted by Cudjoe et al and Boyaci et al, for instance neurotransmitters were not observed in untargeted analyses 10,11 . However, it is possible to extract neurotransmitters with SPME by optimizing the analytical protocol for that speci c group of substances 10,15 .…”

“…Recent work by Boyaci et al 11 has also con rmed Cudjoe et al's 10 observations regarding the complementarity of SPME and MD. Solid-phase microextraction makes it possible to tailor the protocol to the metabolites of interest, as it allows researchers to employ more selective coating and desorption parameters, and it can be coupled with appropriately optimized analytical instrumentation.…”

“…The present article explores chemical biopsy as a new tool that can be used in neurochemistry applications. Previous ex vivo and in vivo investigations of animal brains have demonstrated that some of this technology's unique features may be able to ll the gaps present in existing methods 10,11 . In addition, prior ndings have shown that chemical biopsy is safe for use in laboratory animal studies, and enables the non-depletive analysis of labile endogenous substances, as well as metabolism quenching due to its ability to restrict the access of enzymes to absorbed substances 10,13,15,22 .…”

“…In recent years, solid-phase microextraction (SPME) has been successfully applied in in vivo studies 8 , including brain analyses of macaques 9 and rats [10][11][12][13] . SPME is based on the interaction between compounds in a sample and an extractive sorbent, with extraction taking place until equilibrium is reached between the respective analyte concentrations in the sample and sorbent.…”