MyD88 Deficiency, but Not Gut Microbiota Depletion, Is Sufficient to Modulate the Blood-Brain Barrier Function in the Mediobasal Hypothalamus.

Circumventricular organs (CVOs), including the mediobasal hypothalamus (MBH), have an incomplete blood-brain barrier (BBB). In this study, we determined if the BBB function in the MBH is modulated by the gut microbiota or by the Toll-like receptor (TLR) adapter proteins TRIF or MyD88 signaling. By injecting mice with Evans blue, a marker for BBB permeability, we show that germ-free (GF) and conventionally raised (CONV-R) mice did not differ in the number of Evans blue-positive cells in MBH.