CO-LOCALIZED BUT TARGET-UNRELATED EXPRESSION OF VASOACTIVE INTESTINAL POLYPEPTIDE AND GALANIN IN RAT DORSAL-ROOT GANGLION NEURONS AFTER PERIPHERAL-NERVE CRUSH INJURY

Expression of vasoactive intestinal polypeptide (VIP) and galanin in dorsal root ganglion (DRG) neurons is known to be induced by peripheral nerve injury. We investigated (1) whether VIP and galanin were co-expressed by DRG neurons and (2) whether such neurons innervated specified peripheral targets (visceral, cutaneous or muscular). An antibody to the 200 kDa neurofilament subunit (NF200) was used as a marker for large type-A cells in the DRG. VIP and galanin were respectively observed in 22% and 67% of DRG neurons at the L5 spinal level after crushing of the sciatic nerve. Most VIP-containing neurons were small type-B cells (about 90%) and approximately 95% of VIP-containing neurons also showed galanin-like immunoreactivity. Galanin was expressed by both large type-A and small type-B cells. Immunocytochemistry combined with a retrograde tracer revealed that about 70-80% of the small type-B cells in each sensory division displayed VIP-like immunoreactivity, and that most of the tracer-labeled neurons also expressed galanin. These findings suggest that the expression VIP and/or galanin in response to peripheral nerve crush injury is a property common to visceral, cutaneous and muscular sensory neurons.