Presynaptic inhibition and spinal pain processing in mice:: a possible role of the NKCC1 cation-chloride co-transporter in hyperalgesia

We have examined the role of the NKCC1 sodium-potassium-chloride-cotransporter in the generation of touch-evoked pain. The pain behavior of NKCC1 knockout mice (KO) was studied and compared to that of heterozygous (HE) and wild-type (WT) littermates. NKCC1 KO mice showed an increase in tail flick latencies and a reduction of the duration of pain behavior induced by intradermal capsaicin compared to HE and WT mice. All three groups of animals expressed a normal level of plasma extravasation following capsaicin applications. NKCC1 KO mice showed a reduction in stroking hyperalgesia (touch-evoked pain) compared to WT and HE mice but no differences were detected between the three groups in the expression of punctate hyperalgesia. As the NKCC1 co-transporter is responsible for the generation of presynaptic inhibition between afferent terminals in the spinal cord, these results support the notion that presynaptic interactions between low and high threshold afferents can underlie touch-evoked pain. (C) 2004 Elsevier Ireland Ltd. All rights reserved.