Expression of interleukin-1 beta in rat dorsal root ganglia

The expression of interleukin-lp was examined in dorsal root ganglion (DRG) neurons from adult rats using non-radioactive in Situ hybridization and im munocytochemistry. At all spinal levels, approximately 70% of the DRG neuro ns appeared to express IL-1 beta mRNA: about 80% of these DRG neurons actua lly appeared to produce the IL-lp protein at markedly varying levels. The e xpression of IL-1 beta was found in large as well as in intermediate diamet er sensory neurons but only sporadically in the population of small sensory neurons. The population of IL-1 beta immunopositive sensory neurons includ ed most of the large calretinin-positive la afferents. but only a few of th e small substance P/CGRP positive sensory neurons. In situ hybridization st aining for the detection of type 1 IL-1 beta receptor showed expression of this receptor by most of the sensory neurons as well as by supportive glial -like cells, presumably satellite cells. The functional significance of IL- 1 beta in the DRG neurons needs to be elucidated, but we speculate that IL- 1 beta produced by DRG neurons may be an auto/paracrine signalling molecule in sensory transmission. (C) 2001 Elsevier Science B.V. All rights reserve d.