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INVOLVEMENT OF THE SYMPATHETIC NERVOUS SYSTEM (SNS) IN EXERCISE INDUCED ASTHMA (EIA)

When strenous exercise is performed under ambient laboratory conditions the incidence of EIA is reported to be 80% of the clinically recognized asthmatic population. A heat and water loss, bronchial reflex mechanisms and an imbalance within the autonomic nervous system were suggested to account for EIA.In order to investigate whether the SNS might be involved we have determined plasma nor-adrenaline (NA) as well as the density and affinity of α-and β-adrenoceptors on thrombocytes (THRO) and lymphocytes (LY) in children suffering from EIA and in control children before and after a 7min run. The determination of NA was performed radioenzymatically, that of the adrenoceptors on THRO and LY by use of the radioligands 3[H]-Yohimbine or 125[I]-Cyano-pindolol.- Under resting conditions both asthmatic and non-asthmatic children showed identical plasma levels of NA and an identical density of adrenoceptors on THRO and LY. In response to exercise children with EIA released significantly more NA than the controls.Concomitantly, in children with EIA α-and β-adrenoceptor density remained unchanged by exercise whereas the controls showed a 40% increase in β-, but no increase in α-adrenoceptors.The results may be compatible with the suggestion that either an exaggerated NA release may down regulate β-adrenoceptors in EIA or a functional blockade of β-adrenoceptors may produce a NA release to overcome the blockade.