Release of endomorphin-2 like substances from the rat spinal cord

Release of endomorphin (ENDO)-2 like substances from the dorsal horn of the isolated rat spinal cord was measured by the immobilized-antibody micropro be technique, Spinal cords were removed from anesthetized 4-6 week old rats and superfused with oxygenated Krebs solution at room temperature. Glass m icroprobes coated with ENDO-2 antibodies were inserted into the dorsal horn of the lumbar spinal cord 1.5 mm lateral to the midline to a depth 2.5 mm below the dorsal surface of the cord. Each probe remained in situ for 10 mi n periods before, during and after electrical stimulation applied to the do rsal root entry zone of the same spinal segment. There was no detectable ba sal release of immunoreactive endomorphin-2 like substance (irENDO) from th e dorsal horns during the pre-stimulation, nor following the stimulation pe riod. A significant release of irENDO was measured during the electrical st imulation. These results provide the first evidence of a irEndo release tha t is correlated spatially with the dorsal horn laminae I and II where ENDO- 2-immunoreactive fibers are concentrated in the dorsal horn in response to electrical activation of primary afferent fibers. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.