RESUMEN
BACKGROUND: Whole-brain radiotherapy is a primary treatment for brain tumors and brain metastasis, but it also induces long-term undesired effects. Since cognitive impairment can occur, research on the etiology of secondary effects has focused on the hippocampus. Often overlooked, the hypothalamus controls critical homeostatic functions, some of which are also susceptible after whole-brain radiotherapy. Therefore, using whole-brain irradiation (WBI) in a rat model, we measured neurotransmitters and receptors in the hypothalamus. The prefrontal cortex and brainstem were also analyzed since they are highly connected to the hypothalamus and its regulatory processes. METHODS: Male Wistar rats were exposed to WBI with 11 Gy (Biologically Effective Dose = 72 Gy). After 1 month, we evaluated changes in gamma-aminobutyric acid (GABA), glycine, taurine, aspartate, glutamate, and glutamine in the hypothalamus, prefrontal cortex, and brainstem according to an HPLC method. Ratios of Glutamate/GABA and Glutamine/Glutamate were calculated. Through Western Blott analysis, we measured the expression of GABAa and GABAb receptors, and NR1 and NR2A subunits of NMDA receptors. Changes were analyzed comparing results with sham controls using the non-parametric Mann-Whitney U test (p < 0.05). RESULTS: WBI with 11 Gy induced significantly lower levels of GABA, glycine, taurine, aspartate, and GABAa receptor in the hypothalamus. Also, in the hypothalamus, a higher Glutamate/GABA ratio was found after irradiation. In the prefrontal cortex, WBI induced significant increases of glutamine and glutamate, Glutamine/Glutamate ratio, and increased expression of both GABAa receptor and NMDA receptor NR1 subunit. The brainstem showed no statistically significant changes after irradiation. CONCLUSION: Our findings confirm that WBI can affect rat brain regions differently and opens new avenues for study. After 1 month, WBI decreases inhibitory neurotransmitters and receptors in the hypothalamus and, conversely, increases excitatory neurotransmitters and receptors in the prefrontal cortex. Increments in Glutamate/GABA in the hypothalamus and Glutamine/Glutamate in the frontal cortex indicate a neurochemical imbalance. Found changes could be related to several reported radiotherapy secondary effects, suggesting new prospects for therapeutic targets.
Asunto(s)
Irradiación Craneana , Hipotálamo/efectos de la radiación , Neurotransmisores/análisis , Corteza Prefrontal/efectos de la radiación , Receptores de GABA/análisis , Receptores de N-Metil-D-Aspartato/análisis , Animales , Química Encefálica/efectos de la radiación , Hipotálamo/química , Masculino , Corteza Prefrontal/química , Ratas , Ratas WistarRESUMEN
GABA (γ-aminobutyric acid) is a four carbon non-protein amino acid that is widely distributed in plants, animals and microorganisms. As a metabolic product of plants and microorganisms produced by the decarboxylation of glutamic acid, GABA functions as an inhibitory neurotransmitter in the brain that directly affects the personality and the stress management. A wide range of traditional foods produced by microbial fermentation contain GABA, in which GABA is safe and eco-friendly, and also has the possibility of providing new health-benefited products enriched with GABA. Synthesis of GABA is catalyzed by glutamate decarboxylase, therefore, the optimal fermentation condition is mainly based on the biochemical properties of the enzyme. Major GABA producing microorganisms are lactic acid bacteria (LAB), which make food spoilage pathogens unable to grow and act as probiotics in the gastrointestinal tract. The major factors affecting the production of GABA by microbial fermentation are temperature, pH, fermentation time and different media additives, therefore, these factors are summarized to provide the most up-dated information for effective GABA synthesis. There has been a huge accumulation of knowledge on GABA application for human health accompanying with a demand on natural GABA supply. Only the GABA production by microorganisms can fulfill the demand with GABA-enriched health beneficial foods.
Asunto(s)
Ácido gamma-Aminobutírico/análisis , Glutamato Descarboxilasa/análisis , Neurotransmisores , Receptores de GABA/análisis , Métodos , Estudios RetrospectivosRESUMEN
O fenomeno da excitoxicidade resulta da ativacao excessiva da neurotransmissao glutamatergica, onde pode ocorrer degeneracao neuronal em algumas regioes especificas do SNC, sendo o receptor NMDA o principal canal envolvido na morte neuronal...
Asunto(s)
Humanos , Receptores de Glutamato/análisis , Receptores de GABA/análisis , Etanol/metabolismo , Receptores de Dopamina D1/análisis , Etanol/administración & dosificación , Etanol/envenenamientoRESUMEN
Gamma-aminobutyric acid (GABA) concentrations in seminal plasma and washed spermatozoa from normal donors were assessed by a sensitive radioreceptor assay, and were detectable in both fractions. Specific binding of [3H]-muscimol was shown to be dependent on protein concentration, temperature and incubation time. [3H]-muscimol specific binding to human sperm membranes was significantly inhibited by the GABA type A receptor (GABA(A)) antagonist, bicuculline, and by the GABA(A) agonists, muscimol and isoguvacine, but not by the GABA type B receptor (GABA(B)) agonist baclofen. Scatchard analysis of [3H]-muscimol binding yielded a linear plot consistent with a single population of binding sites with a dissociation constant in the low nanomolar range. Incubation with GABA at a high micromolar concentration for 3 h under capacitating conditions resulted in an increase in the percentage of spermatozoa showing hyperactivated motility as assessed by computerized motility analyser. However, low micromolar concentrations of the GABA(A) agonist, muscimol, were sufficient to significantly increase sperm hyperactivity. These results suggest that the effect of GABA on human sperm motility might be mediated through a specific GABA(A) receptor.