Clarification of the peripherally located F-actin network around the primary afferent neurons

The primary afferent neurons are enriched for F-actin in the peripheries, giving rise to ring-like appearances when stained with fluorescence probes for actin. A variety of data, mainly obtained from in vitro experiments, suggested that the satellite cell (SC) envelopes around sensory neurons may be a candidate for the F-actin positive structures. However, immunohistochemical studies on dorsal root ganglia (DRGs) suggested that F-actin was located exclusively within the cortical regions of the sensory neurons. Given this discrepancy, the present study has reexamined the distribution of F-actin in the DRGs at both the fluorescence light and electron microscopic levels. Double staining of F-actin with S-100beta and neural cell adhesion molecule showed that the fluorescence signals for F-actin around the DRG neurons were restricted to the inner margins of the SC envelope. Subsequent ultrastructural observations, by use of a modified anti-FITC system, demonstrated that the F-actin-positive sites corresponded mostly to the adneuronal SC lamellae, while the cortical cytoskeletons in the neurons seemed to contribute little to the typical F-actin staining. The high concentration of F-actin in the SC envelope has not yet described before, and is thought to assist in understanding the functions of the SCs in the ganglia. (C) 2011 Elsevier B.V. All rights reserved.