Thyroid hormones in the cerebrospinal fluid of the third ventricle of adult female sheep during different periods of reproductive activity

Abstract

Thyroid hormones (THs) are obligatory for transition from breeding season to anestrus in sheep. In this process, THs act during a very limited time of the year and primarily within the brain. In ewes chronically equipped for sampling cerebrospinal fluid (CSF) from the third ventricle, we have characterized the concentrations of total and free thyroxine (T4), triiodothyronine (T3), and total reverse T3 (rT3) in the CSF during breeding season, anestrus and during a critical period required for transition to anestrus (December-March). The total T4, T3, rT3 and free T3 average concentrations (± SEM) in CSF were 1.5 ± 0.07 ng/ml, 14.5 ± 1.2 pg/ml, 43 ± 7.4 pg/ml, and 0.6 ± 0.05 pg/ml, respectively, and all were significantly lower (p < 0.001) than in blood plasma except free T4 (12.6 ± 1.1 pg/ml), which was similar to that in plasma. There was a seasonal trend (p < 0.05) in the concentration of total T3 (highest in December) and free T4 (highest in November) in the CSF that does not follow that in blood plasma. During the period of transition to anestrus the CSF total T3/TT4 molar ratio and free T3/ T4 ratio were significantly lower (p < 0.05 and p < 0.01, respectively) than in blood plasma, while the total rT3/T4 ratio was significantly higher (p < 0.01) at the end of this period (March). Additionally, the CSF total rT3 concentrations were also significantly correlated with the CSF total T4 levels (r = 0.57; p < 0.05). In conclusion, the CSF in sheep may serve as a considerable source of thyroid hormones for neuroendocrine events. The lack of significant changes in THs concentrations in the CSF during the period of transition to anestrus indicate that neither seasonal changes of THs circulating in the blood plasma nor THs circulating in the CSF actively drive the transition to anestrus.

Quercetin and isorhamnetin aglycones are the main metabolites of dietary quercetin in cerebrospinal fluid

“…Our model allowed us to continuously monitor Q metabolites’ presence in urine, blood plasma and CSF following oral administration of dry onion skin. The necessary surgical procedures were developed on the basis of stability of skull structures allowing precise cannula placement for long‐lasting collection of CSF without any side effects for a couple of months . One might claim that pigs, due to their digestive tract similarities to humans, are a better animal model.…”

Seasonal and nutritional changes in the short form of the leptin receptor expression and VEGF system in the choroid plexus, arcuate nucleus, and anterior pituitary in MTS-leptin and resistin-treated sheep

“…Although Szczepkowska et al (2012) concluded that VEGFA may be involved in the photoperiodic plasticity of ChP capillaries, she found only slight changes in VEGFA expression between LD and SD photoperiods in estradiol-implanted and ovariectomized sheep ( Skipor et al, 2010 ). Our study demonstrated in the same animal model that acute fasting (72 h) and photoperiod both modulated VEGFA and VEGR2 protein concentrations.…”

“…Located within the cerebral ventricles, the ChP bridges the blood and CSF. The ChP and CSF are integral in the neuroendocrine regulatory systems that govern seasonal reproduction in animals and particularly in sheep, and ChP operation is strongly guided by photoperiods (Szczepkowska et al, 2020). Notably, protein levels in the ovine ChP related to tight junctions are higher during short days (SD) than LD, leading to differences in the permeability of the BCSFB and thus the ability of molecules to access the CSF from the periphery.…”

Effect of Lipopolysaccharide-Induced Inflammatory Challenge on β-Glucuronidase Activity and the Concentration of Quercetin and Its Metabolites in the Choroid Plexus, Blood Plasma and Cerebrospinal Fluid

“…A schematic diagram of the experiment is presented in Figure 10. One month before the experiment, ewes were implanted with stainless-steel guide cannulas in the third ventricle of the brain for the long-lasting collection of CSF, as described earlier [39]. On the morning of the experiment, ewes were implanted with the jugular vein catheter and placed in individual cages.…”