Hormone pathways in cerebrospinal fluid.

At present, it is difficult to reconcile the relative absence of clear, positive evidence for hormone pathways of the CSF and the ventricular route hypothesis, even when only very particular hormone systems (such as the LHRH system) are examined. One must consider several of the parameters described previously, such as possible entry of hormones into the CSF via the choroid plexus, CVOs and intraventricular nerve endings, or even the possibility that they may cross the blood-brain barrier. Of course, these considerations are important for whatever hormone system is being studied, and there probably may turn out to be several pathways for any particular hormone to access the CSF. In conclusion, despite the fact that there are many acceptable features of the ventricular route hypothesis, more investigation remains to be undertaken in order to fully appreciate the importance of the CSF as an integrator of neuronal and endocrine function.