Reduction of excitation by interleukin-1 beta in rat neocortical slices visualized using infrared-darkfield videomicroscopy.

The cytokine interleukin-1 beta (IL-1 beta) is thought to be critically involved in the neuroendocrine and behavioral changes which occur in response to systemic infection. In the present study, we have employed the novel technique of infrared-darkfield videomicroscopy to examine the effect of IL-1 beta on the intrinsic optical signal (IOS), an indicator of the spread of neuronal excitation and synaptic transmission in the mammalian central nervous system. Low doses of IL-1 beta delivered exogenously to rat neocortical slices produced a reduction of the area of the column-like IOS evoked by orthodromic stimulation. The effect of IL-1 beta was reversible on washout and not mimicked by heat-inactivated IL-1 beta. These results suggest a possible modulatory role of IL-1 beta on synaptic transmission in the rat neocortex which is probably mediated through an activation of GABAA receptors.