Localization of beta-endorphin-like immunoreactivity in the nervous system of the adult newt, Notophthalmus viridescens

Abstract

Using indirect immunofluorescence methods, we have localized for the first time in the newt, Notophthalmus viridescens, beta-endorphin (beta-ep)-like immunoreactivity in the neurons of spinal ganglia (SPG), spinal cord (SPC), as well as in the hypothalamic region of the brain. An examination of serially sectioned SPG showed that the beta-ep-positive neurons, cell bodies, and nerve fibers were distributed at all levels of SPG. Peripheral regions of the perikarya of beta-ep-positive SPG neurons exhibited intense staining for beta-ep, the central nuclear region remaining nonreactive. In SPC, brightly staining fibers were seen entering the afferent nociceptive input areas, namely the Lissauer's tracts, substantia gelatinosa, and the dorsal ascending columns. Dot-fiber immunofluorescence pattern was observed throughout the gray matter of SPC representing beta-ep-positive, secondary sensory neurons as well as interneurons. Also, discrete cluster of neurons located deep in the gray matter of SPC stained positively to beta-ep antisera. This study not only demonstrates for the first time the presence of beta-ep like material in the newt, more specifically in SPG and SPC, but also raises the question of a possible link between beta-ep and newt limb regeneration as previous work has shown that SPG support limb regeneration in a denervated-amputated newt forelimb.