JOINT INFLAMMATION IS REDUCED BY DORSAL RHIZOTOMY AND NOT BY SYMPATHECTOMY OR SPINAL-CORD TRANSECTION

Objectives-To investigate the role of primary afferents, sympathetic p ostganglionic efferents and descending systems on the central control of peripheral inflammation. Methods-Acute inflammation was induced by intra-articular injection of kaolin and carrageenan into the knee join t cavity of the rat. Before the induction of the arthritis, a unilater al dorsal rhizotomy, a chemical (phentolamine) and/or surgical sympath ectomy, or a spinal transection was performed. Joint inflammation (joi nt circumference and thermographic readings) and behavioural signs wer e assessed. Results-Only arthritic animals with a dorsal rhizotomy sho wed a significant reduction of the inflammatory response compared with control arthritic animals. No significant differences in the inflamma tory response occurred following sympathectomy or spinal transection. The animals who received sympathectomy showed similar behavioural mani festations to the arthritic animals. Conclusions-The central terminals of primary afferents are important in the development of acute joint inflammation since dorsal rhizotomy attenuated the inflammatory respon se in the knee joint. The sympathetic nervous system is not involved i n the acute inflammatory phase of this arthritis model. The central pr ocesses controlling acute inflammation involve a local spinal circuit since spinal cord transection at T9 has no effect on the inflammation.