Cutaneous microdialysis in the rat: insertion trauma and effect of anaesthesia studied by laser Doppler perfusion imaging and histamine release.

Microdialysis makes it feasible to study compounds in the extracellular space of cutaneous tissue in vivo. The insertion of the microdialysis probe causes a trauma, which may be anticipated to influence the microdialysis process. The effect of anaesthesia on basal skin blood flow and the trauma in the skin after insertion of a microdialysis probe were investigated. Hairless rats were anaesthetized either with halothane or pentobarbital sodium. Basal skin blood flow and the effect of insertion of a microdialysis probe were measured by laser Doppler perfusion imaging. Trauma-induced histamine release was investigated. Rats anaesthetized with pentobarbital sodium showed a stable skin perfusion in contrast to rats anaesthetized with halothane. A significant increase in blood flow was seen after insertion of the microdialysis probe in the dermis of rats anaesthetized with pentobarbital sodium, while a change in skin blood flow was not observed in rats anaesthetized with halothane. Probe insertion caused histamine release in rats. A minimum equilibration period of 30 min between probe insertion and the start of the experiment is recommended in future studies, allowing immediate events of the trauma to subside and stabilize.