Investigation of the Serotonergic Activity and the Serotonin Content in Serum and Platelet, and the Possible Role of the Serotonin Transporter in Patients with Depression

Abstract

According to the monoamine hypothesis, the development of depression is associated with dysfunctions of the serotonergic system. Alterations in the serotonin transporter gene (5-HTTLPR), the serotonergic activity in the brain, and the content of serotonin (5-HT) have been related to depression and were examined separately by previous studies. This study investigates these parameters in 89 depressed patients and 89 healthy participants. We investigated the serotonergic activity measured by the loudness dependence of auditory evoked potentials (LDAEP). In addition to the examination of the serotonin content (serum and platelet), enzyme-linked immunosorbent assays (ELISA) were used and 5-HTTLPR genotypes were analyzed. We observed a lower serotonin content in patients compared to healthy participants. Further, we noticed a correlation between anxiety and depression-associated symptoms with serotonergic activity. Patients treated with SSRI/SNRI showed decreased contents of serum serotonin compared to patients without any psychotropic medication or other psychotropic medications. Since the serotonergic activity, peripheral serotonin content, and 5-HTTLPR were unrelated, the results suggest independent alterations of central and peripheral serotonergic systems in depression. In line with this finding, serotonergic activity was related to anxiety and depression symptoms. Furthermore, the applied medication seems to influence serum serotonin content in patients with depression.

Electroconvulsive Therapy Modulates Loudness Dependence of Auditory Evoked Potentials: A Pilot MEG Study

“…The neurochemical underpinnings of LDAEP suggest that ECT should lead to a reduction in serotonergic tone within the primary auditory cortex, but this assumption is subject to debate. Studies on the relationship between LDAEP and serotonergic activity have harbored conflicting evidence and perspectives (19, 24, 52, 53). While numerous studies have found that the LDAEP is sensitive to acute changes in serotonergic activity, such as following administration of serotonergic-reuptake inhibitors, other studies have presented contrasting findings (54, 55, 56, 57, 58, 59, 60).…”

Histamine and Serotonin Levels in Bone Marrow Stem Cells Niche as Potential Biomarkers of Systemic Mastocytosis and Myeloproliferative Disorders

“…However, statistical analysis revealed a positive, significant correlation between serotonin level and WBC, and the platelet count. It is known that platelets only transport serotonin produced outside bone marrow by enterochromaffin cells, but are unable to synthesize it [ 18 , 19 ]. Therefore, our findings may confirm the results of studies on the in vivo synthesis of serotonin by its precursors located in bone marrow.…”

Genetic variation of the 5‐HT1A rs6295, 5‐HT2A rs6311, and CNR1 rs1049353 and an altered endocannabinoid system in depressed patients

“…The serotonergic activity in the brain was measured with the noninvasive LDAEP method. The performance and instructions of the LDAEP (cortical and source) can be taken from Obermanns et al (2022).…”

“…In a previous study, compared to healthy participants, we examined the relationship between serotonergic activity (cortical: patients 0.256 ± 0.186/healthy participants 0.252 ± 0.119; p = .855) and the concentration of serotonin in the peripheral blood (serum (patient: 230.9 ± 326.0 ng/mL/healthy participants: 773.8 ± 646.0 ng/mL; p < .001)/platelet (patient: 1113.9 ± 964.1 10 9 /Thr/healthy participants: 2008.8 ± 1026.4 10 9 /Thr; p < .001)) in patients with depression (see Obermanns et al, 2022). Concerning the CNR1 gene, there was a difference among the homozygote GG carriers, the AA allele genotype carriers, and the BDI-II in the group of healthy participants.…”