Opioid activity released from cat spinal cord by sciatic nerve stimulation.

Spinal superfusion was performed in anesthetized cats before and during sciatic nerve stimulation. The superfusates were fractionated on Sephadex G-10 columns and thereafter on electrophoresis and HPLC. The endorphin activity was monitored by radioreceptor and radioimmunoassays. In additional experiments, chromatographic fractions were subjected to enzymatic digestion prior to radioimmunoassay. Nerve stimulation caused a release of at least three different endorphins which separated on electrophoresis, one of which comigrated with [Met]enkephalin-Lys6. The identity of this peptide was further supported by HPLC analysis and radioimmunoassay. Furthermore, enzymatic degradation experiments provided evidence for the presence of enkephalin sequences in all three components released by stimulation. There were also increased dynorphin concentrations during stimulation. These findings suggest that at least two different endorphin systems (enkephalin and dynorphin) are functionally present in spinal cord and may be activated by somatic stimulation.