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Interleukin-1 (IL-1), one of the most important inflammatory cytokines, promotes glia to express intercellular adhesion molecule-1 (ICAM-1) in vitro. IL-1 is known to be produced in situ immediately after brain insults and recently we have found that glia, including astrocytes, express ICAM-1 in vivo following cortical stab wounds. To evaluate the participation of IL-1 beta in posttraumatic ICAM-1 expression on glia in vivo, we performed the following experiments. A cortical stab wound was made in the brain of a mouse. ICAM-1-immunopositive glia began to emerge around the wound from 6 h postlesioning. The number of cells reached a maximum at 48 h and persisted until 7 days postlesioning. Next, a neutralizing monoclonal antibody against IL-1 beta was infused into the wound immediately following the injury. This treatment resulted in a significant reduction of ICAM-1-positive glia at 24 and 48 h postlesioning. We conclude, therefore, that IL-1 beta affects ICAM-1 expression on glia in vivo after experimental brain injury and presumably plays an important role in brain wound repair.

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Coupling of neuronal activity to cerebral blood flow (CBF) is widely accepted, but the exact mechanism is still under investigation. We assessed the responses of CBF coupled with electrical activity over the primary somatosensory cortex (S-I) during electrical stimulation of the contralateral forearm in cats. CBF in S-I was monitored using laser-Doppler flowmetry (LDF), and electrical activity was recorded with a tungsten microelectrode. The effects of varying stimulus intensity and frequency were examined to assess the optimal stimulation parameters. CBF increased within 10 sec after onset of stimulation, sustained the plateau level, and returned to the pre-stimulus level after cessation of stimulation. The maximum response was obtained at 4 Hz under a constant intensity. Optimal stimulus intensity at 4 Hz ranged from 8 to 10 V. At intensity higher than 10 V, CBF increases reached a near-plateau level, while mean arterial blood pressure (MABP) decreased slightly. Electrical activity was recorded at the same restricted area where CBF increased. Low frequency components of the power spectrum of electrical activity increased as the CBF increase became greater. A tight coupling of CBF increases to neuronal activation is suggested, and CBF regulation may be affected by stimulation parameters.