Significance of measured elevation of skin temperature induced by calcitonin gene-related peptide in anaesthetized rats.

To assess whether peripheral changes related to skin temperature rise were induced by ovarian hormone deficiency, we investigated the effects of anaesthesia on calcitonin gene-related peptide (CGRP)- or luteinizing hormone-releasing hormone (LH-RH)-induced elevation of skin temperature in female rats. CGRP was used as an inducer of peripherally-mediated elevation of skin temperature, whereas LH-RH was used as an inducer of centrally-mediated elevation of skin temperature. Intravenous (i.v.) but not intracerebroventricular injection of CGRP (10 microg kg(-1)) or intracerebroventricular but not intravenous injection of LH-RH (10 microg/rat) elevated the skin temperature of unanaesthetized rats restrained in a Ballman's cage. The elevation with LH-RH was completely inhibited by urethane anaesthesia, whereas the elevation with CGRP was not. These results suggested that changes in skin temperature measured under anaesthesia reflected a peripherally rather than a centrally mediated mechanism. The CGRP (1.0-30 microg kg(-1), i.v.)-induced elevation of skin temperature was potentiated in ovariectomized rats and inhibited by pretreatment with a CGRP receptor antagonist CGRP(8-37) (1000 microg kg(-1), i.v.), suggesting that the potentiation may participate in peripheral factors such as a postsynaptic hypersensitivity to CGRP following ovarian hormone deficiency. Thus, measurement of skin temperature in the anaesthetized rat was a useful procedure to seek the peripheral mechanism of potentiation of skin temperature induced by CGRP, thought to be closely related to menopausal hot flashes.