The effect of a unilateral inflammation at the rat's ankle joint on the expression of preprotachykinin-A mRNA and preprosomatostatin mRNA in dorsal root ganglion cells--a study using non-radioactive in situ hybridization.

In rats with an acute (2 days) and chronic (20 days) unilateral ankle joint inflammation (induced by Freund's complete adjuvant), the proportion of dorsal root ganglion cells containing preprotachykinin-A mRNA or preprosomatostatin mRNA was determined using non-radioactive in situ hybridization. At the acute stage of inflammation, the proportion of neurons containing preprotachykinin-A mRNA was similar to that in control rats. At the chronic stage, the proportion of neurons expressing preprotachykinin-A mRNA was significantly higher on the inflamed side than on the contralateral side. The proportion of dorsal root ganglion cells containing preprosomatostatin mRNA did not change. These data suggest that inflammation influences the synthesis of substance P but not of somatostatin in afferent neurons.