Participation of sensory nervous structures in the development of inflammatory reactions

The participation of sensory nervous structures in the development of inflammatory responses in the rat's paw was investigated. Electrical antidromic stimulation of the saphenous or sciatic nerves during 20 min produced an oedematous response in the paw and potentiated the reaction to locally injected carrageenin. On the other hand, decreased responses to carrageenin were observed either when the sciatic nerve was sectioned 15 days before or when a prolonged electrical stimulation (45 min) of the nerve preceded by 1 h the injection of the irritant into the paw. However, if the sciatic nerve was sectioned 30 days before, the inflammatory response to carrageenin in this paw was equivalent to that observed in the contralateral, intact paw. It is suggested that sensory nervous structures might contribute to the development of inflammatory responses, through the release of an active agent, probably from neural origin. This agent would be depleted by prolonged stimulation of sensory nerves. Following partial denervation, the remaining sensory nervous structures in the affected area might develop compensatory mechanisms to influence the institution of the reaction.