THE MOUSE PAW WITHDRAWAL ASSAY - A METHOD FOR DETERMINING THE EFFECT OF CALCITONIN-GENE-RELATED PEPTIDE ON CUTANEOUS HEAT NOCICEPTIVE LATENCY TIME

Previously we have shown that calcitonin gene-related peptide (CGRP) m odulates nociception and the effect of opioid analgesics in the centra l nervous system of mice. Cutaneous primary afferent nerve terminals a lso contain a high concentration of CGRP, however the lack of a suitab le method for assessing cutaneous nociceptive latency changes in the h indpaw skin of the mouse hindered our investigations. We report here o n the development of an assay to investigate the effect of CGRP on noc iception in the dorsal hindpaw skin. Subcutaneous injection of CGRP pr oduced a modest elevation of withdrawal latency time at doses that wer e two orders of magnitude greater than the physiologic levels determin ed in naive animals by radioimmunoassay. This elevation of threshold w as minimal when compared to the elevation produced by mepivacaine. The se results indicate that subcutaneous injection of CGRP into the dorsa l hindpaw skin of the mouse produces a modest increase in paw withdraw al latency times at high, nonphysiologic doses.