The serotonin system controls diverse psychological functions including the regulation of mood, anxiety states, cognition, reward-related behavior. While serotonin signaling take place via 14 differentially regulated serotonin receptors, a single serotonin transporter plays a vital role in controlling the spatial and temporal domains of serotonin’s interactions with these receptors. In humans, SERT expression is thought to be variable due to the 5-HTTLPR, a 43 base pair promoter polymorphism, and a related intervening single nucleotide polymorphism. Variations in SERT expression have been associated with differences in anxiety-related personality traits. We are investigating a mouse model with partial or complete constitutive reductions in SERT expression that similarly exhibits differences in anxiety-like behavior. We previously demonstrated gene dose-dependent reductions in serotonin uptake rates in synaptosomes prepared from a number of brain regions in SERT deficient mice using high-speed chronoamperometry and 30-μm cylindrical carbon fiber microelectrodes. However, maximal uptake rates had to be extrapolated from kinetic curves due to electrode fouling at higher concentrations of serotonin. Here, we investigated the use of boron-doped diamond (BDD) microelectrodes and high-speed chronoamperometry to revisit uptake rates in synaptosomal preparations. Diamond in itself is an insulator due to its sp3-hybridized structure but upon doping with boron during chemical vapor deposition, it displays semiconductor properties. In brain tissue, BDD electrodes showed low background currents, and thus higher signal to noise ratios. These electrodes also showed negligible fouling at higher concentrations of serotonin in brain tissue, as previously demonstrated in gut and invertebrate preparations. We measured a decrease in uptake rates associated with constitutive reductions in SERT expression in oxygenated striatal and hippocampal synaptosomes. Specifically, serotonin uptake was reduced by ~70% in hippocampal tissue and ~50% in striatal tissue in SERT+/- mice compared to SERT+/+ mice. Maximal uptake (Vmax) and affinity for serotonin (Km) in striatal synaptosomes from SERT+/- were 60 pmol/wet wt/min and 2 μM, respectively. These are in good agreement with our previously published results using carbon fiber microelectrodes. Given the robust nature of BDD sensors, these might represent an alternative to carbon fiber electrodes with the advantage of better evaluating serotonin neurotransmission in brain under conditions when higher concentrations of serotonin might be anticipated upon stimulation.