Functional Change of Brain Serotonergic Activity and Free Tryptophan in the Plasma of Depressed Women

Felipe Vázquez-Estupiñan,Rocío Herrera-Márquez,José Antonio Mondragón-Herrera,Gabriel Manjarrez-Gutiérrez,Guillermina Lara-Pérez

doi:10.4236/ojd.2019.81002

Abstract

The main objective was to show the decrement of serotoninergic brain activity in depressed women, through the analyses of the slope amplitude of N1/P2 components of the auditory-evoked potentials (AEP), and the measurement of the L-tryptophan free fraction in plasma (FFT). This cross-sectional study was carried out in 60 women, 30 depressed and 30 normal controls. Both groups were measured FFT, glucose, and neutral amino acids (NAA) levels; besides performing AEP to analyses the N1/P2 slope amplitude. It was found a lengthening in the slope amplitude of N1/P2 components of AEP in the group of depressed women, and despite that the level of FFT was low, there were no changes between bound fraction and the total L-Trp. The former suggests a decrease in serotonergic brain activity in the group of depressed women. Otherwise, since the auditory cortex response to sound is regulated by serotonergic innervation, it was expected a change in the behavior of AEP in the group of depressed patients. Thus, the slope amplitude of N1/P2 components of the AEP and the measurement of FFT have proved to be a good clinical indicators of the serotonergic neurotransmission state in the brain of depressed patients, and in another clinical conditions where brain serotonin is involved.

Highlights

The main objective was to show the decrement of serotoninergic brain activity in depressed women, through the analyses of the slope amplitude of N1/P2 components of the auditory-evoked potentials (AEP), and the measurement of the L-tryptophan free fraction in plasma (FFT)
The main objective of this study was to show the decrement of serotoninergic brain activity in depressed women, through the analyses of the slope amplitude of N1/P2 components of the auditory-evoked potentials, and the measurement of the L-tryptophan free fraction in plasma
Biochemical results showed a significantly low level of the free fraction of L-Trp in the depressed women group; fact that initially suggests a low transport of tryptophan to the brain and as a result, a low synthesis of serotonin which leads to a serotoninergic activity reduction

Summary

Introduction

There are some hypotheses related to the dysfunction of some networks and neurotransmission neuronal systems inside the limbic area, and the cortex; which are based on different polymorphisms that may lead to metabolism dysfunction, and transport alterations of monoamines, serotonin, dopamine, norepinephrine, glutamate, and gamma-amino-butyric acid (GABA) along these systems (Nestler et al, 2002; Meltzer, 1990; Dunlop & Nemeroff, 2007; Nutt, 2006; Sullivan et al, 2000; Lohoff, 2010; Pehrson & Sanchez, 2014). Depression must not be viewed as a single disease, but as a syndrome triggered by different causes and physiopathology (Nestler et al, 2002). Different attempts have been made to establish several subtypes of depression, based on certain groups of symptoms (Akiskal, 2000; Blazer, 2000); these subtypes are based solely on symptomatic differences, and there is as yet no evidence that they reflect different underlying disease states

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