Indications for a brain uptake of labelled vasopressin and ocytocin and the problem of the blood-brain barrier.

Fifteen seconds after intracarotid injection of [125J]-lysine vasopressin, [3H]-ocytocin, tritiated water or [3H]-inulin, the distribution of radioactivity in 18 regions of the rat brain and in the anterior pituitary was determined. Comparing the concentration of the different tracers (in % of injected radioactivity per g brain tissue), it is assumed that a small amount of the labelled neurohormones is taken up by the brain, indicating a penetration of the blood-brain barrier and/or an accumulation within the structures of the barrier system.