Activation of BDNF-TrkB Signaling in Specific Structures of the Sheep Brain by Kynurenic Acid.

Fluctuations in kynurenic acid (KYNA) and brain-derived neurotrophic factor (BDNF) levels in the brain reflect its neurological status. The aim of the study was to investigate the effect of transiently elevated KYNA concentrations in the cerebroventricular circulation on the expression of BDNF and its high-affinity tropomyosin-related kinase receptor B (TrkB) in specific structures of the sheep brain. Intracerebroventricularly cannulated anestrous sheep were subjected to a series of four 30 min infusions of KYNA: 4 × 5 μg/60 μL/30 min (KYNA20, = 6) and 4 × 25 μg/60 μL/30 min (KYNA100, = 6) or a control infusion ( = 6), at 30 min intervals.

Amylase intrapancreatic infusion delays insulin release during an intravenous glucose tolerance test, proof of acini-islet-acinar interactions.

Background: The possible existence of an acini-islet-acinar (AIA) reflex, involving mutual amylase and insulin interactions, was investigated in the current acute experiment on pigs.

Aim: To confirm the existence of an AIA reflex and justify the placement of the exocrine and endocrine pancreatic components within the same organ.

Methods: The study was performed on six pigs under general anesthesia.

Kynurenic Acid Modulates the Expression of Genes and the Activity of Cellular Antioxidant Enzymes in the Hypothalamus and Hippocampus in Sheep.

Kynurenic acid (KYNA), a tryptophan metabolite, is believed to exert neuromodulatory and neuroprotective effects in the brain. This study aimed to examine KYNA's capacity to modify gene expression and the activity of cellular antioxidant enzymes in specific structures of the sheep brain. Anestrous sheep were infused intracerebroventricularly with two KYNA doses-lower (4 × 5 μg/60 μL/30 min, KYNA20) and higher (4 × 25 μg/60 μL/30 min, KYNA100)-at 30 min intervals.

Central Stimulatory Effect of Kynurenic Acid on BDNF-TrkB Signaling and BER Enzymatic Activity in the Hippocampal CA1 Field in Sheep.

Deficiency of neurotrophic factors and oxidative DNA damage are common causes of many neurodegenerative diseases. Recently, the importance of kynurenic acid (KYNA), an active metabolite of tryptophan, has increased as a neuroprotective molecule in the brain. Therefore, the present study tested the hypothesis that centrally acting KYNA would positively affect: (1) brain-derived neurotrophic factor (BDNF)-tyrosine receptor kinase B (TrkB) signaling and (2) selected base excision repair (BER) pathway enzymes activities in the hippocampal CA1 field in sheep.

Involvement of neurosteroids in the control of prolactin secretion in sheep under basal, stressful and pregnancy conditions.

Prolactin (PRL) secretion by the anterior pituitary (AP) is responsive to changes in physiological conditions and many external factors that also affect brain neurosteroid levels. This study tested the hypothesis that neurosteroids can affect PRL secretion in sheep under basal, stressful and advanced pregnancy conditions. In Experiment 1, luteal-phase sheep were subjected to a three-day series of intracerebroventricular (icv.

Involvement of neurosteroids in the control of hypothalamic-pituitary-adrenal axis activity in pregnant sheep under basal and stressful conditions.

Neurosteroids are synthesized locally in the brain, where they can modify neuronal functionality depending on the physiological state. A high correlation was demonstrated between the increasing activity of the hypothalamic-pituitary-adrenal (HPA) axis and allopregnanolone (AL) concentration in the cerebrospinal fluid in sheep during pregnancy. Therefore, the present study tested the hypothesis that blocking neurosteroid synthesis in the brain of a pregnant sheep would affect HPA axis activity under both basal and stressful conditions.

Effects of allopregnanolone on central reproductive functions in sheep under natural and stressful conditions.

Reproductive functions may be affected by internal and external factors that are integrated in the central nervous system (CNS). Stressful stimuli induce the neuroendocrine response of the hypothalamic-pituitary-adrenal axis, as well as the synthesis of the neurosteroid allopregnanolone (AL) in the brain. This study tested the hypothesis that centrally administered AL could affect the expression of certain genes involved in reproductive functions at the hypothalamus and pituitary levels, as well as pulsatile gonadotropin secretion in sheep under both natural and stressful conditions.