Fig. 1.

Mechanisms of central leptin access. Schematic drawing depicting the border at the level of the median eminence (ME) and arcuate nucleus (ARC) as an example to show different mechanisms of central leptin access. A. Saturable transport of leptin across the blood brain barrier (BBB). B. Direct access of leptin receptor neurons to the circulation via projections close to fenestrated capillaries (perivascular space) in circumventricular organs (CVO’s, e.g. median eminence, area postrema, organum vasculosum). C. Leptin transport via tanycytes into cerebrospinal fluid (CSF) in the ventricular space (e.g. the third ventricle, 3V).