Serum level of serotonin during rest and during exercise in paraplegic patients

Abstract

The purpose of this study was to evaluate the serum level of serotonin (5-HT) during rest and response to exercise in subjects with spinal cord injury (SCI) with di erent levels of physical activity. Twenty-®ve male subjects with traumatic paraplegia, the neurological levels being between T1 and T12, volunteered for the study. They were divided into two groups matched for age, weight and time since injury, according to the level of physical activity: 14 inactive and 11 subjects regularly involved in sports activity and considered active. They all performed a maximal spiroergometric test with an arm crank ergometer. Two samples of blood were collected for 5-HT determination, during rest (PRE) and immediately after exercise test (POST). Serum 5-HT concentration was measured by high performance liquid chromatography using electrochemical detection (HPLC-ED). The results showed that peak oxygen uptake (V . O 2peak ) was higher in the active group (27.08+2.60 vs 18.89+5.58 mL.kg 71 .min 71 , P50.001). There were no signi®cant di erences between the inactive and active groups for the 5-HT PRE (respectively 176.96 and 193.73 ng.mL 71 , P40.05) or POST values (275.44 vs 311.05 ng.mL 71 , P40.05). Both groups showed an increment in 5-HT after maximal exercise, but only in the active group it reached statistical signi®cance (Wilcoxon test, P50.02). Our results show that chronic paraplegic individuals have normal resting serum serotonin levels and normal response to exercise. The relationship between training status, mood elevation and 5-HT in SCI could not be established in the present study, and further investigation is needed to clarify this issue.

Post exercise hypotension is not mediated by the serotonergic system in borderline hypertensive individuals

“…However, human studies that have examined the contribution of the ␤-endorphins to PEH by blocking the system with naloxone have elicited contradictory results. 7,10 The concentrations of peripherally circulating 5-HT in the present study were considerably lower than those found in other studies (eg, Steinberg et al 19 ). We attribute this to our control to 5-HT release from platelets.…”

Effects of Oral Branched‐Chain Amino Acids (BCAAs) Intake on Muscular and Central Fatigue During an Incremental Exercise

“…This neuropharmacological result could be due to attenuation of the elevation in a TRP:BCAAs ratio by administration of BCCAs (Burke, 2001;Nemet and Eliakim, 2007). It is well documented that prolonged physical exercise increases serotonin levels (Steinberg et al, 1998) rather than intermittent exercise (Eichelberger and Bilodeau, 2007). This is mainly due to slower oxidation of BCAAs during the recovery period (Nemet and Eliakim, 2007) and subsequently, it prevents an increase of plasma TRP concentration (Steinberg et al, 1998).…”

“…It is well documented that prolonged physical exercise increases serotonin levels (Steinberg et al, 1998) rather than intermittent exercise (Eichelberger and Bilodeau, 2007). This is mainly due to slower oxidation of BCAAs during the recovery period (Nemet and Eliakim, 2007) and subsequently, it prevents an increase of plasma TRP concentration (Steinberg et al, 1998). However, in our study the plasma serotonin level was higher in both trials compared to baseline value (165.7 ± 13.8 ng/ml; Table 1) and normal range (68-232 ng/ml), indicating that during exercise the participants reached the point of 'central fatigue', due to the serotonergic system.…”

Potential causes, mechanisms, and implications of post exercise hypotension

“…The mechanism for this inhibition of sympathetic outflow is unknown. Interestingly, serotonin has been found to increase during exercise in brain tissue of rats 98 and in blood samples of humans 99 and may be involved in PEH.…”