Abstract
Brain 5-HT neurotransmission has been described to be down-regulated in depressed
people, and also suspected to be changed in overtraining state, the consequence of
long-term physical overloading and stress in athletes. We studied brain serotonin
(5-HT) transporter binding i.e., 5-HT reuptake with the specific radioligand (123-I-labelled
2β-carbomethoxy-3β[4-iodopenyl]-nortropane, Nor-β‐CIT), and with single photon emission
tomography (SPET) in severely overtrained athletes and their controls at the baseline
and after a one-year recovery period. Twelve overtrained (6 women and 6 men, mean
age 27 yrs, range 16 - 39 yrs) and 11 healthy (6 women, 5 men, 26 yrs, 20 - 39 yrs)
athletes were examined. Overtrained athletes 1) had suffered from an unexplained decrement
in physical performance and fatigue for several weeks to many months and continued
to have the same symptoms even after a recovery time of weeks to months, 2) had been
examined to be otherwise healthy, and 3) had a suitable training history for overtraining.
Nor-β‐CIT SPET was acquired 5 min, and 3, 6, and 24 h after the injection of the radioligand.
5-HT reuptake in ml/ml in midbrain (raphe nuclei) was calculated as (midbrain - cerebellum)/cerebellum.
According to two-way analysis of variance, no changes inside the groups or group differences
in 5-HT reuptake were found. Male athletes had significantly higher 5-HT reuptake
than female athletes at the baseline (p = 0.034). The overtrained athletes were moderately
depressed, while their scores in standardized Hamilton and Montgomery-Åsberg Depression
Rating Scales were 16 ± 2 (mean ± SEM, range 8 - 29) and 17 ± 2 (7 - 28), respectively.
In the CA, the scores were 6 ± 1 (range 2 - 18) and 6 ± 2 (1 - 19), respectively.
5-HT reuptake did not correlate with the depression scores either in the whole group
or in the OA. The finding of the present study does not support the idea of long-term
changes in 5-HT neurotransmission in overtraining state, in this case serotonin reuptake
in midbrain, the regulating area of brain serotonin neurotransmission. Furthermore,
depression of overtrained athletes may be its own variant having no correlation with
5-HT reuptake in midbrain. Sex may have effect on chronic stress response at the brain
level in athletes, which may be a confusing factor in the overtraining studies, and
has to be taken into consideration in the future.
Key words
Neurotransmission - overtraining - SPET - Nor-β-CIT
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A. Uusitalo
Helsinki University Central Hospital, HUSLAB Division of Clinical Physiology and Nuclear
Medicine
P. O. Box 340
00029 Hus
Finland
Fax: + 35 89 47 17 66 78
Email: arja.uusitalo@hus.fi