Aktuelle Neurologie 2005; 32 - P414
DOI: 10.1055/s-2005-919447

Are prostaglandines involved in the sympathetic-nociceptive interaction in humans?

R Maag 1, J Schattschneider 1, I zum Buttel 1, A Binder 1, J Ludwig 1, G Wasner 1, R Baron 1
  • 1Kiel

Aim of investigation: Iontophoresis of norepinephrine in capsaicin-treated skin is followed by an increase in spontaneous and evoked pains. It is unclear whether norepinephrine acts directly on adrenergic receptors located on nociceptive afferents or triggers prostaglandine release from sympathetic postganglionic terminals as suggested by animal studies. The effect of norepinephrine on capsaicin-induced pain prior and after inhibition of cyclooxygenase was studied.

Methods: In 10 healthy subjects norepinephrine or placebo was iontophorised after topical application of capsaicin in the forearm. The effect of iontophoresis on cutaneous blood flow was controlled by laser Doppler. Furthermore, norepinephrine was given in capsaicin-treated skin one hour after placebo-controlled i.v. injection of acetylsalicylic acid. Spontaneous pain, mechanical hyperalgesia as well as warm and heat pain thresholds were measured prior and after iontophoresis. The local skin temperature was kept constant at 30°C. The inhibtion cyclooxygenase was controlled by measuring Acetylcholin induced vasodilatation. The study was performed in agreement with the Declaration of Helsinki.

Results: Iontophoresis of norepinephrine did enhance spontaneous pain and the intensity of mechanical hyperalgesia in capsaicin treated skin significantlly. Furtheron, a significant decrease in heat pain thresholds was found. There was no significant difference in norepinephrine induced somatosensory changes whether saline or acetylsalicylic acid was injected.

Conclusion: We found no evidence that norepinephrine acts on nociceptive afferents via the release of prostaglandines from postganglionic terminals in capsaicin-sensitized human skin. Thus, a direct action of norepinephrine on adreneric receptors in the membrane of the afferent fibers is most likely.

Supported by, the Deutsche Forschungsgemeinschaft (Ba 1921/1–3), the BMBF (01EM01/04), the Alexander von Humboldt-Stifung and Pfizer Deutschland (unrestricted educational grant).