“…However, these data cannot serve as direct evidence that the brain is the only source of CSF monoamines. Indeed, we cannot exclude that monoamines enter the CSF not only from the brain neurons but from the bloodstream as well in the absence of a blood–brain barrier for monoamines in the perinatal period [ 14 , 29 , 30 ], with also taking into account the possibility of a metabolism between the CSF and blood in the choroid plexus in the lateral ventricles, in circumventricular organs, and the area of the caudal venous sinus even in adult animals [ 7 ]. In addition, one should not forget the fact that there are such important sources of monoamines as the adrenal glands, gastrointestinal tract, and the peripheral sympathetic nervous system [ 31 , 32 , 33 ].…”