Follicle-stimulating hormone regulates Notch signalling in the seminiferous epithelium of continuously and seasonally breeding rodents.

CONTEXT: Juxtacrine (contact-dependent) communication between the cells of seminiferous epithelium mediated by Notch signalling is of importance for the proper course of spermatogenesis in mammals. AIMS: The present study was designed to evaluate the role of follicle-stimulating hormone (FSH) in the regulation of Notch signalling in rodent seminiferous epithelium. METHODS: We explored the effects (1) of pharmacological inhibition of the hypothalamus-pituitary-gonadal (HPG) axis and FSH replacement in pubertal rats, and (2) of photoinhibition of HPG axis followed by FSH substitution in seasonally breeding rodents, bank voles, on Notch pathway activity. Experiments on isolated rat Sertoli cells exposed to FSH were also performed. Gene and protein expressions of Notch pathway components were analysed using RT-qPCR, western blot and immunohistochemistry/immunofluorescence. KEY RESULTS: Distribution patterns of Notch pathway proteins in bank vole and rat seminiferous epithelium were comparable; however, levels of activated Notch1 and Notch3, hairy/enhancer of split 1 (HES1) and hairy/enhancer of split-related with YRPW motif 1 (HEY1) in bank voles were dependent on the length of the photoperiod. In response to FSH similar changes in these proteins were found in both species, indicating that FSH is a negative regulator of Notch pathway activity in seminiferous epithelium. CONCLUSIONS: Our results support a common mechanism of FSH action on Notch pathway during onset and recrudescence of spermatogenesis in rodents. IMPLICATIONS: Interaction between FSH signalling and Notch pathway in Sertoli cells may be involved in spermatogenic activity changes of the testes occurring during puberty or photoperiod shift in continuously and seasonally breeding rodents, respectively.

Glutamate as a Stressoric Factor for the Ex Vivo Release of Catecholamines from the Rabbit Medial Prefrontal Cortex (mPFC).

One of the major roles of glutamic acid (Glu) is to serve as an excitatory neurotransmitter within the central nervous system (CNS). This amino acid influences the activity of several brain areas, including the thalamus, brainstem, spinal cord, basal ganglia, and pons. Catecholamines (CAs) are synthesized in the brain and adrenal medulla and by some sympathetic nerve fibers. CAs, including dopamine (DA), norepinephrine (NE), and epinephrine (E), are the principal neurotransmitters that mediate a variety of CNS functions, such as motor control, cognition, emotion, memory processing, pain, stress, and endocrine modulation. This study aims to investigate the effects of the application of various Glu concentrates (5, 50, and 200 µM) on CAs release from rabbit medial prefrontal cortex (mPFC) slices and compare any resulting correlations with CAs released from the hypothalamus during 90 min of incubation. Medial prefrontal cortex samples were dissected from decapitated, twelve-week-old female rabbits. The results demonstrated that Glu differentially influences the direct release of CAs from the mPFC and the indirect release of CAs from the hypothalamus. When under stress, the hypothalamus, a central brain structure of the HPA axis, induces and adapts such processes. Generally, there was an inhibitory effect of Glu on CAs release from mPFC slices. Our findings show that the effect arises from Glu's action on higher-order motivational structures, which may indicate its contribution to the stress response by modulating the amount of CAs released.

Glutamic Acid Decarboxylase Concentration Changes in Response to Stress and Altered Availability of Glutamic Acid in Rabbit (Oryctolagus cuniculus) Brain Limbic Structures.

Glutamic acid decarboxylase (GAD) is an enzyme that catalyses the formation of γ-aminobutyric acid (GABA), the most important inhibitory neurotransmitter, from glutamic acid (Glu), which is considered the most important excitatory transmitter in the central and peripheral nervous systems. GAD is a key enzyme that provides a balance between Glu and GABA concentration. Hence, it can be assumed that if the GAD executes the synthesis of GABA from Glu, it is important in the stress response, and thus also in triggering the emotional states of the body that accompany stress. The aim of the study was to investigate the concentration of the GAD in motivational structures in the brain of the rabbit (Oryctolagus cuniculus) under altered homeostatic conditions caused by stress and variable availability of Glu. Summarising, the experimental results clearly showed variable concentrations of GAD in the motivational structures of the rabbit brain. The highest concentration of GAD was found in the hypothalamus, which suggests a strong effect of Glu and GABA on the activity of this brain structure. The GAD concentrations in individual experimental groups depended to a greater extent on blocking the activity of glutamate receptors than on the effects of a single stress exposure. The results obtained clearly support the possibility that a rapid change in the concentration of GAD could shift bodily responses to quickly achieve homeostasis, especially in this species. Further studies are necessary to reveal the role of the Glu-GAD-GABA system in the modulation of stress situations as well as in body homeostasis.