Herpes Simplex Virus 1‐Mediated Transfer of Preproenkephalin A in Rat Dorsal Root Ganglia

: Recombinant herpes simplex virus‐1 encoding the rat preproenkephalin A (HSVLatEnk1) was generated for driving the expression of preproenkephalin A‐derived peptides in dorsal root ganglia of rats in vivo. Three weeks after infection via the hind footpads, quantitative RT‐PCR and in situ hybridization experiments showed a strong expression of preproenkephalin A mRNA in lumbar dorsal root ganglia. In addition, a 40–160% increase in radioimmunoassayable Met‐enkephalin‐like material concentrations was found in the dorsal spinal cord and dorsal root ganglia, respectively, at the lumbar level in HSVLatEnk1‐infected rats as compared with animals infected with β‐galactosidase‐encoding recombinant herpes simplex virus‐1 or control rats. These data demonstrate the efficacy of the preproenkephalin A encoding vector and suggest that it should help in elucidating the role of Met‐enkephalin‐containing primary afferent fibers in pain transmission and/or control.