Abstract
Cholecystokinin (CCK) is an important gastointestinal hormone as well as a neurotransmitter. Two types of CCK receptors (types A and B) have been cloned. CCK-A receptors are present only in certain regions including the hypothalamus, whereas CCK-B receptors are widely distributed throughout the central nervous system. Otsuka Long-Evans Tokushima Fatty (OLETF) rats express CCK-B receptors and CCK genes normally in the brain but lack CCK-A receptors because of a genetic abnormality. These animals become stout, and develop diabetes mellitus after about 18 weeks of age. We have clarified that these animals experience deterioration of the circadian rhythmicity of body temperature and thermoregulatory ability under thermal stress from this age. In the present study, we examined thermoregulatory responsiveness, e.g., vasomotor responses and shivering, to thermal stimulation of the hypothalamus in these animals. A thermode was implanted into the preoptic area and anterior hypothalamus (PO/AH) under anesthesia. Rectal temperature and paw and tail skin temperatures were monitored by thermistors. EMG of the neck muscle was also measured. There were no differences between threshold temperatures of vasomotor and shivering. These results indicate that OLETF rats possess normal thermoregulatory responsiveness to thermal stimulation of the PO/AH. It is suggested that the abnormality of circadian rhythm and the deterioration of thermoregulatory ability of these animals might be due to dysesthesia caused by diabetes mellitus. [Jpn J Physiol 54 Suppl:S229 (2004)]
