LAUSR

Keeping the internal environment constant in a continuously changing external environment, i.e. the maintenance of homeostasis is crucial for the living organisms and it is served by several mechanisms. Interleukin-1 (IL-1) is one of the most important cytokines, peptide molecules that are responsible for the communication among the immune, neural and other cells of the organism in immune and inflammatory processes. Of the two isoforms of this primary cytokine, the ‘beta’ form appears to be biologically a lot more important. The IL-1b is known to have numerous functional effects both in the immune and nervous systems, and its role has already been shown in homeostatic regulatory processes as well [1]. The target area of our present series of experiments was the anterior cingulate cortex which is known to be essential in motivational, emotional and cognitive control mechanisms. As part of the limbic system, it is supposed to be also involved in the organization of homeostatic processes. In microelectrophysiological experiments of our laboratory, the functional presence of IL-1b responsive neural cells has been elucidated in this cortical area. Based on all the above, the goal of the highlighted study [2] was to reveal whether cytokine mechanisms of the cingulate cortex are important in the central regulation of homeostasis. To do so, changes in food and water intake, body temperature, and other metabolic functions, i.e. homeostatic effects of direct bilateral microinjection of IL-1b into the cingulate cortex of adult male Wistar rats have been investigated. To clarify the role of cyclooxygenase (COX) – mediated mechanisms in the mode of the postulated action of IL-1b, the effect of intracerebral pretreatment by the COX-inhibitor paracetamol was tested in our study. Guide cannulas for the IL-1b or vehicle microinjections were implanted on the surface of the dura above the cingulate cortex in a stereotaxic operation under ketamine anesthesia. One week later, IL-1b; paracetamol or sterile phosphate-buffered saline (PBS), in the sham control animals, were administered into the cingulate cortex as bilateral microinjections through the previously implanted guide cannulas (Figure 1). Food and water consumption of the rats were monitored for one day after the microinjections: short(2 h), medium(12 h) and long-term (24 h) measurements were performed. Animals were divided into four groups in these experiments: half of both the cytokine-treated and the control animals received paracetamol pretreatment 25 minutes before the administration of IL-1b or PBS. These experiments were carried out after 24 hours of food deprivation. Body temperature of the same four groups of animals was measured rectally, just before and two hours after the intracerebral microinjections, by means of a digital thermometer. In order to examine the blood glucose levels of cytokine treated and control rats, a standard glucose tolerance test was performed 12 hours following the food deprivation. Measurements were carried out right before and 20 minutes after the cerebral microinjections of IL-1b or PBS, as well as 9, 18, 30, 60 and 120 minutes after the sugar load. Blood samples were taken from the tail vein of the rats and blood glucose levels were determined electrochemically by means of a semi-automatic glucometer. Relevant plasma metabolites (total cholesterol, HDL, LDH, triglycerides, uric acid) of the animals were also determined following 12 hours of food deprivation. Blood samples were obtained after decapitation of the rats 20