Chronic intermittent hypoxia induces expression of phospho-PKC substrates in rat pre-Bötzinger complex / 生理学报

The pre-Bötzinger complex (pre-BötC) residing in the ventrolateral medulla oblongata, is thought to be the kernel of respiratory rhythmogenesis. Episodic hypoxia exerts respiratory long-term facilitation, being recognized as electrophysiological characteristic of respiratory motor neuroplasticity. Our previous study demonstrated up-regulated expression of phospho-protein kinase C θ (P-PKCθ) in the pre-BötC of rats receiving chronic intermittent hypoxic (CIH) challenge. The present study was aimed to examine subcellular distribution of P-PKC substrates (P-PKCsub) and explore PKC down-stream targeting proteins in the pre-BötC in normoxic and CIH rats. Using neurokinin-1 receptor (NK1R) as a marker of the pre-BötC, P-PKCsub immunoreactivity was revealed by immunofluorescence and immuno-electron microscopic double-labeling in the pre-BötC. Western blot was applied to analyze P-PKCsub proteins in ventrolateral medulla, containing the pre-BötC. The results showed that NK1R immunoreactivity (NK1R-ir) was expressed mainly along plasma membranes of somata and processes, outlining pre-BötC neurons under the light microscope. P-PKCsub immunoreactive (P-PKCsub-ir) fluorophores in dot-like appearance appeared in somata and processes. Some were in close apposition to plasma membranes. A majority of P-PKCsub-ir neurons was found with NK1R-ir. CIH challenge up-regulated the expression of P-PKCsub proteins in the ventrolateral medulla. Under the electron microscope, NK1R-ir product was found to distribute along the inner membrane surfaces of somata and dendrites. P-PKCsub-ir gold particles were located in somata and dendrites, and some were distributed along the inner membrane surfaces, as well as in the endoplasmic reticulum and postsynaptic dense body. These results suggest that CIH challenge up-regulates the expression of P-PKCsub proteins, probably including some receptor proteins in the postsynaptic membrane, which may contribute to respiratory neuroplasticity via activation of PKCθ in the pre-BötC.

Environmental Enrichment Promotes Antioxidant Effect in the Ventrolateral Medulla and Kidney of Renovascular Hypertensive Rats / O Enriquecimento Ambiental Promove Efeito Antioxidante no Bulbo Ventrolateral e Rins de Roedores com Hipertensão Renovascular

Abstract Background: Arterial hypertension is a precursor to the development of heart and renal failure, furthermore is associated with elevated oxidative markers. Environmental enrichment of rodents increases performance in memory tasks, also appears to exert an antioxidant effect in the hippocampus of normotensive rats. Objectives: Evaluate the effect of environmental enrichment on oxidative stress in the ventrolateral medulla, heart, and kidneys of renovascular hypertensive rats. Methods: Forty male Fischer rats (6 weeks old) were divided into four groups: normotensive standard condition (Sham-St), normotensive enriched environment (Sham-EE), hypertensive standard condition (2K1C-St), and hypertensive enriched environment (2K1C-EE). Animals were kept in enriched or standard cages for four weeks after all animals were euthanized. The level of significance was at p < 0.05. Results: 2K1C-St group presented higher mean arterial pressure (mmHg) 147.0 (122.0; 187.0) compared to Sham-St 101.0 (94.0; 109.0) and Sham-EE 106.0 (90.8; 117.8). Ventrolateral medulla from 2K1C-EE had higher superoxide dismutase (SOD) (49.1 ± 7.9 U/mg ptn) and catalase activity (0.8 ± 0.4 U/mg ptn) compared to SOD (24.1 ± 9.8 U/mg ptn) and catalase activity (0.3 ± 0.1 U/mg ptn) in 2K1C-St. 2K1C-EE presented lower lipid oxidation (0.39 ± 0.06 nmol/mg ptn) than 2K1C-St (0.53 ± 0.22 nmol/mg ptn) in ventrolateral medulla. Furthermore, the kidneys of 2K1C-EE (11.9 ± 2.3 U/mg ptn) animals presented higher superoxide-dismutase activity than those of 2K1C-St animals (9.1 ± 2.3 U/mg ptn). Conclusion: Environmental enrichment induced an antioxidant effect in the ventrolateral medulla and kidneys that contributes to reducing oxidative damage among hypertensive rats.

Resumo Fundamento: A hipertensão arterial é um precursor para o desenvolvimento da insuficiência cardíaca e renal e, além disso, está associada com o aumento dos marcadores oxidativos. O enriquecimento ambiental dos roedores melhora o desempenho em tarefas de memória, e também parece ter um efeito antioxidante sobre o hipocampo dos ratos normotensos. Objetivos: Avaliar o efeito do enriquecimento ambiental sobre o estresse oxidativo no bulbo ventrolateral, coração, e rins de ratos com hipertensão renovascular. Métodos: Quarenta ratos machos, tipo Fischer (6 semanas de idade), foram divididos em quatro grupos: normotensos em condições padrão (Sham-CP), normotensos em ambiente enriquecido (Sham-AE), hipertensos em condições padrão (2R1C-CP), e hipertensos em ambiente enriquecido (2R1C-AE). Os animais foram mantidos em gaiolas enriquecidas ou padrão durante quatro semanas e, por fim, todos os animais foram eutanasiados. O nível de significância foi p < 0,05. Resultados: O grupo 2R1C-CP apresentou pressão arterial média maior (mmHg) 147,0 (122,0; 187,0) quando comparado com os grupos Sham-CP 101,0 (94,0; 109,0) e Sham-AE 106,0 (90,8; 117,8). Observou-se maior atividade das enzimas superóxido dismutase (SOD) (49,1 ± 7,9 U/mg ptn) e da catalase (0,8 ± 0,4 U/mg ptn) no bulbo ventrolateral do grupo 2R1C-AE, em relação à atividade da SOD (24,1 ± 9,8 U/mg ptn) e da catalase (0,3 ± 0,1 U/mg ptn) no grupo 2R1C-CP. No grupo 2R1C-AE, a oxidação lipídica no bulbo ventrolateral foi menor (0,39 ± 0,06 nmol/mg ptn) quando comparado com o grupo 2R1C-CP (0,53 ± 0,22 nmol/mg ptn). Ademais, foi observada maior atividade das enzimas superóxido dismutase nos rins dos animais 2R1C-AE (11,9 ± 2,3 U/mg ptn) em relação aos animais 2R1C-CP (9,1 ± 2,3 U/mg ptn). Conclusão: O enriquecimento ambiental provocou efeito antioxidante no bulbo ventrolateral e nos rins, o que contribuiu para a redução do dano oxidante nos ratos hipertensos.

Angiotensin-II-induced reactive oxygen species along the SFO-PVN-RVLM pathway: implications in neurogenic hypertension

Neurogenic hypertension has been the subject of extensive research worldwide. This review is based on the premise that some forms of neurogenic hypertension are caused in part by the formation of angiotensin-II (Ang-II)-induced reactive oxygen species along the subfornical organ-paraventricular nucleus of the hypothalamus-rostral ventrolateral medulla pathway (SFO-PVN-RVLM pathway). We will discuss the recent contribution of our laboratory and others regarding the mechanisms by which neurons in the SFO (an important circumventricular organ) are activated by Ang-II, how the SFO communicates with two other important areas involved in sympathetic activity regulation (PVN and RVLM) and how Ang-II-induced reactive oxygen species participate along the SFO-PVN-RVLM pathway in the pathogenesis of neurogenic hypertension.

The expression of GABA(A) receptor alpha1 and GABA(B) receptor 1 in medulla oblongata solitary nucleus and ambiguous nucleus in the cases of tramadol intoxication / 法医学杂志

OBJECTIVE@#To observe the expression of GABA(A) receptor alpha1 (GABA(A)alpha1) and GABA(B) receptor 1 (GABA(B)1) in human medulla oblongata solitary nucleus and ambiguous nucleus due to tramadol-induced death.@*METHODS@#GABA(A)alpha1 and GABA(B)1 were detected by immunohistochemical SP method in tramadol-induced death group and control group. All results were evaluated by images analysis system.@*RESULTS@#Low expression of GABA(A)alpha1 and GABA(B)1 were detected in solitary nucleus and ambiguous nucleus in the control brain tissue. In cases of tramadol-induced death, the expression of GABA(A)alpha1 and GABA(B)1 significantly increased.@*CONCLUSION@#The mechanism of tramadol intoxication death could be caused by respiratory depression induced by over-expression of GABA(A)alpha1 and GABA(B)1 in medulla oblongata solitary nucleus and ambiguous nucleus.

Differential brain angiotensin-II type I receptor expression in hypertensive rats

Blood-borne angiotensin-II (Ang-II) has profound effects in the brain. We tested the hypothesis that Ang-II-dependent hypertension involves differential Ang-II type I (AT1) receptors expression in the subfornical organ (SFO) and the rostral ventrolateral medulla (RVLM). Male Wistar rats were implanted with 14-day osmotic minipump filled with Ang-II (150 ng/kg/min) or saline. AT1 receptor mRNA levels were detected in the SFO and RVLM by reverse transcription-polymerase chain reaction (RT-PCR). Ang-II caused hypertension (134 +/- 10 mmHg vs. 98 +/- 9 mmHg, n = 9, p < 0.05). RT-PCR revealed that Ang-II infusion induced increased AT1 receptor mRNA levels in RVLM and decreased in SFO. Our data suggest that Ang-II-induced hypertension involves differential expression of brain AT1 receptors.

Study on the change of bFGF in reticular formation of medulla oblongata after primary brain-stem injury / 法医学杂志

OBJECTIVE@#To study the effect of primary brain-stem injury on the expression of basic fibroblast growth factor (bFGF) in the reticular formation of medulla oblongata.@*METHODS@#Immunohistochemical SABC was used to study the change of bFGF expression in the reticular formation of medulla oblongata after brain-stem injury by striking.@*RESULTS@#The numbers of positive cells and positive intensity of the study group in the reticular formation of medulla oblongata were significantly elevated than those of the control group and the postmortem injury group.@*CONCLUSION@#The expression of bFGF is elevated in reticular formation after brain-stem injury.

Evidence for neuronal release of isotopically labelled glycine from the rat ventral medullary surface in vivo

Spontaneous and stimulus-induced release of isotopically labelled glycine was studied in the superfused rat dorsal or ventral medullary surface in vivo. Superfusion of the ventral medullary surface of anesthetized (urethane, 1.2 g/kg, ip) male adult Wistar rats (250-350 g) with high K+ (40 mM) surrogate cerebrospinal fluid (CSF) produced an average increase of 45 per cent over the spontaneous efflux of exogenously applied glycine (N = 5, P<0.01). In experiments in which the calcium of the CSF was replaced by an equimolar amount of magnesium, the increase in glycine efflux in response to high K+ was reduced to 15 per cent, a value not statistically different from that observed in control experiments (N = 6). Veratridine stimulation evoked a large (80 per cent) increase in glycine efflux (N = 5, P<0.001), which was inhibited by tetrodotoxin. High potassium or veratridine failed to modify spontaneous release of glycine on the dorsal medullary surface. Results obtained in control experiments showed that neither high K+ nor veratridine is effective in modifying spontaneous efflux of [(3)H]-leucine or [(3)H]-inulin on the ventral or dorsal medullary surface. These data support the hypothesis that glycine is a neurotransmitter on the ventral medullary surface and that it may be part of neural pathways involved in cardiorespiratory regulation present in this region.