N1/P2 component of auditory evoked potential reflect changes of the brain serotonin biosynthesis in rats

Abstract

It is known that L-tryptophan stimulates serotonin synthesis in the brain and serotonergic neuronal activity. Also, the N1/P2 component of auditory evoked potential (AEP) is a good indicator of this activity in the auditory cortex. In the present work, we examined the effect of the L-tryptophan administration on electric activity of the auditory cortex recorded as the N1/P2 component of the AEP in adult male rats. The effect of serotonergic agonists or antagonists was also tested. The results showed that indeed L-tryptophan was able to induce a drastic change in auditory cortex electric activity, reducing very significantly the amplitude of the N1/P2 component of the AEP. Quipazine maleate had a similar effect as L-tryptophan and the serotonergic antagonist spiperone induced an increase in the N1/P2 amplitude. These results show how an isolated nutrient is able to induce significant changes in brain auditory cortical function, through stimulation of serotonin synthesis. Besides, they add evidence about the important role of serotonergic neurotransmission modulating sensory cortical activity and that the N1/P2 component of AEPs represent a useful noninvasive indicator of brain serotonin tone.

Loudness Dependence of Auditory Evoked Potentials as Indicator of Central Serotonergic Neurotransmission: Simultaneous Electrophysiological Recordings and In Vivo Microdialysis in the Rat Primary Auditory Cortex

“…However, anatomical findings correspond in both species: granular cells in layer IV of the auditory cortex of rats and humans receive direct projections from the thalamus (McCormick and Prince, 1985;Di and Barth, 1993). Changes in serotonergic and noradrenergic neurotransmission precipitate changes in AEP in both species (Manjarrez et al, 2001(Manjarrez et al, , 2005Keedy et al, 2007). The AEP of rats shows similarities to that of humans in terms of latency, waveform, and duration (Sambeth et al, 2003).…”

Another Abnormal Trait in the Serotonin Metabolism Path in Intrauterine Growth-Restricted Infants

“…The results of the different somatometric measurements carried out in the IUGR infants confirmed a symmetrical delay of the physical growth, which constitutes an accepted clinical manifestation [2,3,[21][22][23] . On the other hand, it is interesting to mention that fetal growthrestricted infants were fed alone with maternal milk to free demand from birth on and had a sufficient catch-up in the growth curves that allowed some of them to reach the growth rate of controls during the nursing period [30] .…”

“…We therefore proposed the hypothesis that infants with IUGR may have a different binding kinetics of L-Trp to albumin, which might be responsible for the raised plasma L-Trp available to be transported to the brain that may reflect an abnormality of the aforementioned mechanism. This in turn elevates the brain serotonin synthesis rate and neuronal activity as it has been reported, modifying cerebral cortical sensory response [20,21] .…”

Psychophysiological Markers of Anxiety Disorders and Anxiety Symptoms

“…Administrating quipazine maleate-a 5-HT 2 receptor agonistreduced the amplitude of N1/P2 components whereas administrating spiperone-a 5-HT 1A receptor antagonist-increased the N1/P2 amplitude in rats (Manjarrez et al, 2005). Administrating the precursor of 5-HT, L-tryptophan, was associated with the reduced amplitude of N1/P2 components (Manjarrez et al, 2005). Other studies showed that the LDAEP was inversely correlated with the concentration of 5-hydroxyindoleacetic acid (main metabolite of serotonin) in cerebrospinal fluid (von Knorring et al, 1981).…”

“…Initial evidence that linked the LDAEP and the serotonergic system came from animal studies (O'Neill et al, 2008). Administrating quipazine maleate-a 5-HT 2 receptor agonistreduced the amplitude of N1/P2 components whereas administrating spiperone-a 5-HT 1A receptor antagonist-increased the N1/P2 amplitude in rats (Manjarrez et al, 2005). Administrating the precursor of 5-HT, L-tryptophan, was associated with the reduced amplitude of N1/P2 components (Manjarrez et al, 2005).…”