european college of sport science

Thursday, June 25th, 2009
dilatation and sympatholysis by binding to endothelial ATP selective P2Y2 purinergic receptors and stimulating the vascular endothelium
to release vasodilator-sympatholytic substances, including nitric oxide, prostaglandins and endothelium-derived hyperpolarization
factors.
Support: Copenhagen Hospital System, Novo Nordisk Foundation and Lundbeck Foundation.
ROLE OF ENDOTHELIUM AND SKELETAL MUSCLE DERIVED VASODILATORS
HELLSTEN, Y.
UNIVERSITY OF COPENHAGEN
Role of endothelium and skeletal muscle derived vasodilators
in exercise hyperaemia
Ylva Hellsten
Copenhagen Muscle Research Centre, Department of Exercise and Sport Science, University of Copenhagen, Universitetsparken 13, DK-
2100 Copenhagen Denmark
In skeletal muscle, blood flow may increase more than 30-fold from rest to exercise, with a close match between the rate of flow and
oxygen demand. The precise regulation is achieved by a balance between sympathetic vasoconstriction and locally formed vasodilators,
but also vasoconstrictors and compounds that induce sympatholysis are involved . Studies using pharmacological inhibition of single or
multiple vasodilator systems in humans have revealed that the compounds nitric oxide (NO), prostaglandins (PG’s), 11, 12 eicosatrienoic
acid (11, 12 EETs), adenosine and ATP are regulators of muscle blood flow. Such studies have also demonstrated that there is interaction
between vasodilators where a specific vasodilator can compensate for the impaired release of another, i.e. redundancy. Evidence for
redundancy exists between NO and PG’s and between NO and 11, 12 EETs. In addition, some compounds exert or extend their vasoactive
effects by inducing the release of vasodilators. Examples of this are the effects of ATP and adenosine in causing the release of NO and
PG’s. In fact, evidence point at that release of nitric oxide and prostaglandins is the primary mechanism by which adenosine regulates
exercise hyperaemia and that a direct effect of adenosine on adenosine receptors on smooth muscle cells appear to be of less importance.
Thus, several vasodilators of importance for muscle blood flow control have been identified and evidence point at that the precise
regulation of flow is the result of a close interplay between these vasodilators. Nevertheless, simultaneous inhibition of multiple known
vasodilator systems has only been found to reduce exercise hyperemia in humans by ~30%, which could suggest the existence of yet
unidentified vasodilators.
Support: Danish Medical Research Council, Novo Nordisk Foundation, Lundbeck Foundation
08:30 - 10:00
Invited symposia
IS-BM08 Laterality and assymetries in sports
MECHANISMS UNDERLYING FUNCTIONAL CHANGES IN THE PRIMARY MOTOR CORTEX IPSILATERAL TO AN ACTIVE
ARM
PEREZ, M.A.
UNIVERSITY OF PITTSBURGH
Performance of a unimanual motor task results in functional changes in both primary motor cortices (M1s). The neuronal mechanisms
controlling the corticospinal output originating in the M1 ipsilateral to a moving arm remain poorly understood (1). Gaining insight into
these mechanisms may contribute to a better understanding of how unimanual and bimanual movements are controlled (2,3,4,5).
During this presentation I will review several electrophysiological markers of motor cortical function measured at rest and during different
levels of unilateral and bilateral finger, wrist and elbow voluntary movements by using transcranial magnetic stimulation (TMS). These
electrophysiological markers include: motor-evoked potential (MEP) recruitment curves, short-interval intracortical inhibition (SICI), interhemispheric
inhibition measured by a paired-pulse TMS paradigm and by the ipsilateral cortical silent period (iSP), and the influence of
interhemispheric inhibition over SICI.
Our results have shown activity-dependent changes in SICI in M1 ipsilateral, interhemispheric inhibition from M1 contralateral to M1
ipsilateral, and in the influence of interhemispheric inhibition over SICI. Differences are observed between responses evoked from distal
and proximal representations in the primary motor cortex (4,5). Altogether our findings indicate that interactions between GABAergic
intracortical circuits mediating SICI and interhemispheric glutamatergic projections between M1s partly contribute to control activitydependent
changes in corticospinal output in the M1 ipsilateral to a moving arm during voluntary movement by the opposite arm.
1. Carson RG. Brain Res Brain Res Rev 49:641–662, 2005
2. Hortobágyi et al. J Neurophysiol 90: 2451-2459, 2003
3. Muellbacher W et al. Clin Neurophysiol 111: 344-349, 2000
4. Perez and Cohen. J Neurosci 28: 5631-5640, 2008
5. Perez and Cohen. Cortex (in press), 2009
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