Carrageenan-induced inflammation alters the content of i-cGMP and i-cAMP in the dorsal horn of the spinal cord.

Hindpaw injections of carrageenan (CARRA) decreased paw withdrawal latencies to radiant heat and increased hindpaw edema. At the peak of hyperalgesia, the content of immunoreactive guanosine 3',5'-cyclic monophosphate (i-cGMP) was increased, while immunoreactive adenosine 3',5'-cyclic monophosphate (i-cAMP) was decreased in lumbar, but not cervical dorsal horn. In general, the content of i-cGMP in the dorsal horn was correlated with thermal hyperalgesia throughout the course of this model. These results indicate that a peripheral inflammation alters the content of i-cGMP and i-cAMP in the spinal cord and, further, suggest that these nucleotides are involved in the modulation of hyperalgesia in the spinal cord.