IN-VIVO RELEASE OF INTERLEUKIN-1-BETA INTO HYPOTHALAMIC EXTRACELLULARFLUID IN RATS - EFFECTS OF REPEATED SAMPLING

Interleukin-1 beta (Il-1 beta) concentrations in extracellular fluid ( ECF) withdrawn at 10-min intervals through a push-pull cannula (PPC) l ocated in the hypothalamus were studied in freely behaving male rats f or 1 h at 24 and 72 h and again at 7 days after PPC implantation. Il-1 beta concentrations in ECF were similar in the latter. However, when ECF was sampled at 3 h and again 7 days after PPC implantation, Il-1 b eta concentrations were greatly elevated at 7 days when compared to al l other intervals. These results demonstrate how the relationships bet ween Il-1 beta measured in ECF and the conditions of measurement appea r to be integral parts of a whole intracerebral system: cytokine conce ntrations appear to be inextricably bound to intrahypothalamic conditi ons created by the sampling device presence and frequency of use.