Using in situ hybridization with riboprobes the distribution of α2A-, α2B- and α2C-adrenoceptor mRNAs were studied in normal rat dorsal root ganglia and after unilateral peripheral nerve injury (total nerve transection) or inflammation. The most common adrenoceptor mRNA was of the α2C subtype (almost 80% of all neuron profiles) followed by the α2A subtype (almost 20%), whereas α2B-adrenoceptor mRNA was only found in small numbers of neuron profiles. The most dramatic effect of peripheral nerve injury was observed for the α2A-adrenoceptor mRNA, which increased to 45% of all neuron profiles. In contrast, α2C adrenoceptor mRNA showed a small decrease in this situation. Carrageenan-induced peripheral inflammation did not affect the percentage of α2A- or α2C-adrenoceptor mRNA-positive profiles. These findings suggest that, if any of the α2 adrenoceptor, the α2A subtype represents the most likely candidate in DRG neurons to be involved in sympathetically maintained pain.
aDepartment of Neuroscience, Karolinska Institutet, S 171 77 Stockholm, Sweden
bDepartment of Pharmacology, University of California, Irvine, Irvine, CA 92717, USA
* Corresponding author. Tel.: +46-468-728-7070; fax: +46-468-331-692
Received December 14, 1998; received in revised form June 14, 1999; accepted August 20, 1999
1 Present address: Department of Pharmacology and Toxicology, Medical College of Virginia, Richmond, VA 23219, USA.