The role of somatostatin and a stable analogue, sandostatin (Octreotide), on the responses of spinal cord neurones in vivo was investigated in the rat. Electrical C-fibre stimulation was used as a model of acute nociception and the response to subcutaneous formalin was used as a model of longer term events. Intrathecal pre-treatment with sandostatin and somatostatin did not alter the C-fibre response, wind up or A beta responses of the cells. However, intrathecal pre-treatment with sandostatin and somatostatin inhibited both the first and second phases of the formalin response dose dependently. Thus, sandostatin (20 micrograms) and somatostatin (150 micrograms) inhibited the first phase (66 +/- 12% inhibition and 52 +/- 13% respectively) and second phase (91 +/- 2% inhibition and 39 +/- 16% inhibition respectively). The second phase of the formalin response was more sensitive to somatostatin and sandostatin than the first. Sandostatin was approximately 400 times more potent than somatostatin on the second phase of the response. Subcutaneous sandostatin (100 mg/kg) significantly inhibited both the first and second phase of the formalin response whereas the local peripheral administration of sandostatin (20 micrograms) only inhibited the second phase of the formalin response.