EFFECTS OF CALCITONIN-GENE-RELATED PEPTIDE-(8-37) ON WITHDRAWAL RESPONSES IN RATS WITH INFLAMMATION

The present study was performed to explore the effect of subcutaneous injection of carrageenan into the rat plantar region on hindpaw edema formation and the latency of hindpaw withdrawal to presumed nociceptiv e stimulation. Subcutaneous injection of carrageenan into the left hin dpaw induced a significant increase in the volume of the left hindpaw, leaving the right side unaffected. In addition, we found a bilateral decrease in hindpaw withdrawal latency to heat and mechanical, but not to cold stimulation. The decreased bilateral hindpaw withdrawal laten cy to heat stimulation lasted for 14 days after carrageenan injection. The decreased bilateral hindpaw withdrawal latency to mechanical stim ulation lasted for 2 days after the injection, then reversed and incre ased from day 3 to 14. Intrathecal injection of either 10 nmol of calc itonin gene-related peptide 8-37 or 26.6 nmol of morphine induced sign ificant bilateral increases in hindpaw withdrawal latency, which were more pronounced with the morphine. The results show that experimentall y induced unilateral hindpaw inflammation induces a bilateral decrease in hindpaw withdrawal latencies to presumed nociceptive stimulation w hile the sensory systems for heat and mechanical stimulation were diff erently affected after carrageenan injection. (C) 1998 Elsevier Scienc e B.V.