Effects of repeated surgical stress on daily changes of body core temperature in mice

Daily body core temperature rhythm has been known to become blunted for several days following intra-abdominal implantation of biotelemetry transmitters in small rodents and about a week is required for re-establishment of stable body core temperature oscillation. In the present study carried out on mice it was found that a repetition of the same minor surgical intervention (laparotomy) several days apart could speed up the stabilization of body temperature oscillations. Melatonin supplied with the drinking water continuously was found to speed up the return of stable daily body temperature rhythm further on consecutive laparotomies, while daily injections of methylprednisolone resulted in some delay in the development of stable body core temperature oscillations. It is concluded that in C57BL/6 mice possessing low plasma levels of melatonin exhibit an adaptive response to repeated stresses influencing the dynamics of daily body temperature rhythm.