Changes in spinal cholecystokinin release after peripheral axotomy

The gene expression of cholecystokinin (CCK), a neuropeptide with anti-opio id properties, has been reported to be upregulated in some primary sensory neurons after a peripheral nerve lesion. We have recently demonstrated that the upregulation of CCK mRNA is not accompanied by an increased potassium- evoked release of CCK-like immunoreactivity (CCK-LI) 2-4 weeks after a comp lete transection of the sciatic nerve. The potassium-evoked release of CCK- LI at earlier and later time points has, however, not been studied. The aim of the present in vivo microdialysis study was to monitor how the basal an d stimulated extracellular level of CCK in the dorsal horn of the spinal co rd is affected at various time points after a complete transection of the s ciatic nerve (axotomy). During the first week after transection of the scia tic nerve a tendency towards an elevation of the potassium-induced (100 mM in the perfusion fluid) release of spinal CCK-LI was observed. In contrast, no potassium-induced release of CCK-LI could be detected 2-3 weeks and 2 m onths after axotomy. No significant effect was observed on the basal extrac ellular levels of CCK-LI in the dorsal horn. The present study provides fur ther support for the notion that the adaptive changes in the dorsal horn 2 weeks and later after a deafferentiation injury do not include an increased release of CCK. NeuroReport 12:49-52 (C) 2001 Lippincott Williams & Wilkin s.