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Abstract

During fever, cardiovascular changes have been seen to accompany the change in body temperature. There is evidence to implicate an area of the brain called the ventral septal area/ diagonal band of Broca (VSA/DBB) in both thermoregulation and cardiovascular control. This thesis investigates the possibility that neurons of the VSA/DBB which are known to be involved in thermoregulation during fever, may also be involved in some aspect of cardiovascular control during fever induced by endotoxin. The investigation was performed by infusing lidocaine HC1 into the VSA of freely moving conscious rats while the parameters of body temperature, heart rate and mean arterial blood pressure were monitored. Body temperature and cardiovascular parameters were measured in two separate groups of rats. The first set of experiments before brain infusion with lidocaine show that endotoxin has an effect on all of the above parameters. Body temperature showed the typical hypothermic phase followed by an increase to febrile levels in response to injection of endotoxin. Mean arterial blood pressure showed a biphasic response to injection of endotoxin as did heart rate. In the second set of experiments, the animals were injected with endotoxin while the animals received infusion of lidocaine into the VSA/DBB. The results show lidocaine infusion had no significant effect on body temperature, heart rate or mean arterial blood pressure in response to endotoxin. In conclusion the results do not support the idea that the VSA mediates an interaction between body temperature and mean arterial blood pressure, but neither does the data necessarily refute the possibility that the VSA is the site of this interaction.