Postnatal expression of interleukin-6 (IL-6) and IL-6 receptor (IL-6R) mRNAs in rat sympathetic and sensory ganglia

The postnatal expression of interleukin-6 (IL-6) and IL-6 receptor (IL-6R) mRNAs in superior cervical ganglia (SCG) and dorsal root ganglia (DRG) of normal rats were studied by using RT-PCR. IL-6 and IL-6R transcripts were found in both these peripheral nervous system (PNS) tissues and their expression was differentially regulated. In sensory ganglia, a strong upregulation (12-fold) of the IL-6R mRNA occurred between postnatal day 2 and day 20, staying al this elevated level until adulthood (day 70). During the same period the IL-6 mRNA increased to a lesser extent (3-fold). In SCG, both transcripts undergo only a minor induction (2-fold) during postnatal development. To identify the cellular source of IL-6 and its receptor mRNAs in both PNS tissues, a sensitive non-radioactive in situ hybridization technique was used. Both mRNAs could be localized predominantly in the neuronal cell bodies in the sympathetic and sensory ganglia. In addition, IL-6R mRNA positive cells were found located along the axon outside the DRG, and are likely to be Schwann cells. The same cells were negative for IL-6 mRNA. These findings support the concept of IL-6 as a regulator of neuronal survival and differentiation in the central and peripheral nervous system.