BEHAVIORAL THERMOREGULATION IN MICE INOCULATED WITH INFLUENZA-VIRUS

Mice housed at 30-degrees-C and inoculated with a mouse-adapted influenza virus show a fall in body temperature (T(b)) and a decrease in food intake to almost 0 grams per day. This study tested whether the fall in T(b) could be accounted for by the decreased food intake and whether the fall in T(b) was due to a decrease of thermoregulatory set point or to an inability to maintain T(b) at set point level. The fall in T(b) of influenza-infected mice was greater than that of food-deprived mice. When food deprived, mice given access to a thermal gradient increased their preference for warmer areas in the gradient and, as a result, T(b) did not fall as much as T(b) of starved mice not given access to a thermal gradient. When infected with influenza virus, mice given a thermal gradient decreased T(b), less and at a slower rale than mice not given a gradient. However, this fall in T(b) of influenza-infected mice was greater than that of food-deprived mice given a thermal gradient. Mice given a thermal gradient increased their preference for the warmer temperatures after inoculation; this returned to preinoculation preference for cooler temperatures during the later days of infection despite a continuous fall in T(b). Influenza-infected mice given a thermal gradient survived significantly fewer days than infected mice not given a thermal gradient. We conclude that the influenza-induced fall of T(b) in mice cannot be explained solely by the decrease in food intake, and is partially due to a decrease in thermoregulatory set point.