Anti-somatostatin antisera, but neither a somatostatin agonist (octreotide) nor antagonist (CYCAM), attenuates hyperalgesia in the rat.

Somatostatin has been reported to have both nociceptive and antinociceptive roles in sensory transmission in the spinal cord. In this study, antisera against SOM (alpha-SOM), a somatostatin antagonist (CYCAM) and a somatostatin agonist (octreotide), were evaluated for their role in thermal and mechanical hyperalgesia in a model of carrageenan-induced inflammatory pain in the rat. Intrathecal administration of alpha-SOM prior to hindpaw inflammation dose-dependently attenuated thermal and mechanical hyperalgesia and the increase in paw size for up to 4 h following injury. Administration of alpha-SOM 3 h following injury had no effect. Intrathecal administration of octreotide or CYCAM prior to or following injection of carrageenan had no effect on any measure. It is suggested that the lack of effect of octreotide and CYCAM resulted from low affinity for the SOM receptor subtypes in the rat spinal cord. The attenuation of hyperalgesia and paw size produced by alpha-SOM may have resulted from attenuation of somatostatin's role in producing a dorsal root reflex that modulates the increase in paw size following injury.