TNFα diminishes amplitudes of CSD and lowers their propagation velocity dose-dependently. In order to investigate the underlying mechanisms, we recorded in spontaneously breathing anesthetized adult rats (sodium thiopentone, 100 mg/kg, i.p.) CSD in cerebral cortex with two pairs of glass micropipettes (distance 5-6 mm) at depths of 1200 µm. CSD was elicited by a microinjection of 1 M KCl (tip diameter 5 µm, 100 kPa, 300 ms) into the grey matter. In one subset of rats we administered 2.5 µg of a TNF receptor 1 antagonist, in another subset 0.25 µg of a TNF receptor 2 antagonist, and in a third subset 1 µM bicuculline topical to the cortical surface for one hour each, tested for CSD and then we applied 5 ng TNFα and continued the recordings. After sacrificing the animals, the cortices were stained with antibodies against TNF receptor 1 or 2 and the localization of both receptors was determined.

The pretreatment with the TNF receptor 1 antagonist did not interfere with the inhibitory effect of 5 ng TNFα on CSD. However, the blockade of the TNF receptor 2 completely abolished the effects of TNFα. Histological observation showed that TNF receptor 2 is mostly located on neuronal but not on glial cellular membranes. The blockade of GABA_A receptors by bicuculline abolished the effects of TNFα on CSD as well, thus indicating that inhibitory neurons might be involved in the action of TNFα on CSD.

These results suggest that TNFα might act on CSD via the activation of inhibitory interneurons.