Past experiments in which researchers had elecrically stimulated various circumventricular
organs in the brain of mice, including the SFO, had yielded inconsistent results.
These reports support the present results that indicate increased water intake in the second hour of the 2 h feeding period in large-type goats fed on dry forage for 2 h twice daily is the result of increases in plasma osmolality, caused by the ruminal absorption of salts from the consumed feed, that in turn bypassed the blood-brain barrier and activated the osmosensitive neurons in the circumventricular
Particular attention should be paid to lesions in circumventricular
organs and the optic nerve head, since in both regions the blood-brain barrier is less tight than in other regions of the CNS, and AQP-4 is highly expressed at these sites.
However, structures such as the area postrema, median eminence, portions of the hypothalamus, and other circumventricular
organs that lie outside the blood-brain barrier play an integral role in the vomiting reflex.
Other neural afferents and transduction of humoral messages at circumventricular
organs have also been suggested as routes for innate immune system influences on the CNS (Bluthe, Michaud, Kelley, & Dantzer, 1996; Shibata & Blatteis, 1991).