The Effects of Tryptophan Enhancement and Depletion on Plasma Catecholamine Levels in Healthy Individuals

Serotonergic Modulation of Neurovascular Transmission: A Focus on Prejunctional 5-HT Receptors/Mechanisms

5-Hydroxytryptamine (5-HT), or serotonin, plays a crucial role as a neuromodulator and/or neurotransmitter of several nervous system functions. Its actions are complex, and depend on multiple factors, including the type of effector or receptor activated. Briefly, 5-HT can activate: (i) metabotropic (G-protein-coupled) receptors to promote inhibition (5-HT₁, 5-HT₅) or activation (5-HT₄, 5-HT₆, 5-HT₇) of adenylate cyclase, as well as activation (5-HT₂) of phospholipase C; and (ii) ionotropic receptor (5-HT₃), a ligand-gated Na⁺/K⁺ channel. Regarding blood pressure regulation (and beyond the intricacy of central 5-HT effects), this monoamine also exerts direct postjunctional (on vascular smooth muscle and endothelium) or indirect prejunctional (on autonomic and sensory perivascular nerves) effects. At the prejunctional level, 5-HT can facilitate or preclude the release of autonomic (e.g., noradrenaline and acetylcholine) or sensory (e.g., calcitonin gene-related peptide) neurotransmitters facilitating hypertensive or hypotensive effects. Hence, we cannot formulate a specific impact of 5-HT on blood pressure level, since an increase or decrease in neurotransmitter release would be favoured, depending on the type of prejunctional receptor involved. This review summarizes and discusses the current knowledge on the prejunctional mechanisms involved in blood pressure regulation by 5-HT and its impact on some vascular-related diseases.

The clinical value of aquaporin-4 in children with hand, foot, and mouth disease and the effect of magnesium sulfate on its expression: a prospective randomized clinical trial

To evaluate the clinical value of aquaporin-4 (AQP-4) in hand, foot, and mouth disease (HFMD) and to evaluate therapeutic efficacy of magnesium sulfate (MgSO4) and its effect on AQP-4 expression. Children with HFMD were divided into a common group, a severe group and a critical group according to Chinese guidelines; children in the critical group were further divided into two subgroups: routine treatment group and MgSO4 group. Outcome measures included systolic blood pressure (SBP), Heart rate (HR), the levels of AQP-4, interleukin-6 (IL-6), norepinephrine (NE), and neuron-specific enolase (NSE). Serum AQP-4, IL-6, NE, and NSE levels varied significantly among the critical, severe, and common groups before and after treatment. There were no significant differences in AQP-4 levels in cerebrospinal fluid (CSF) between the critical and severe groups before and after treatment; however, CSF AQP-4 levels in these two groups were higher than those in the common group before treatment. Serum and CSF AQP-4 levels in convalescence decreased significantly in the critical and severe groups. SBP, HR and serum AQP-4, IL-6, NE, NSE levels, but not CSF AQP-4 levels, were significantly lower in MgSO4 group than in the routine treatment group. AQP-4 in serum, but not in CSF, is a candidate biomarker for evaluating the severity and prognosis of HFMD; MgSO4 can provide protection on children with critical HFMD.

Distinct expression and clinical value of aquaporin 4 in children with hand, foot and mouth disease caused by enterovirus 71

Brain dysfunction is a prerequisite for critical complications in children with hand, foot, and mouth disease (HFMD). Aquaporin 4 (AQP-4) may be involved in the pathological process of cerebral oedema and injury in children with severe and critical HFMD. This study aimed to assess the association of AQP-4 with the severity of enterovirus 71 (EV71)-associated HFMD. Children with EV71-infected HFMD were divided into a common group (clinical stage 1), a severe group (clinical stage 2), and a critical group (clinical stage 3) according to Chinese guidelines. The levels of AQP-4, interleukin-6 (IL-6), norepinephrine (NE), and neuron-specific enolase (NSE) before and after treatment were tested. Serum AQP-4, IL-6, NE, and NSE levels showed significant differences among the critical, severe, and common groups before and after treatment (P<0.01). No significant differences in AQP-4 levels in cerebrospinal fluid (CSF) were observed between the critical and severe groups before and after treatment, but the CSF AQP-4 levels in these two groups were higher than those in the common group before treatment (P<0.01). Serum AQP-4 levels, but not CSF AQP-4 levels, closely correlated with serum IL-6, NE, and NSE levels. These results suggest that the level of AQP-4 in serum, but not in CSF, is a candidate biomarker for evaluating the severity and prognosis of EV71-associated HFMD.