Patterns of membrane potentials and distributions of the medullary respiratory neurons in the decerebrate rat

We analyzed the membrane potential of 161 respiratory neurons in the medulla of decerebrate rats which were paralyzed and ventilated. Three types of inspiratory (I) neurons were observed: those displaying progressive depolarization in inspiration (augmenting I neurons), those which gradually repolarized after maximal depolarization at the onset of inspiration (decrementing I neurons) and those exhibiting a plateau or bell-shaped membrane potential trajectory throughout inspiration (I-all neurons). Three types of expiratory (E) neurons were also encountered: those in which the membrane potential progressively depolarized (augmenting E neurons), those in which the membrane potential repolarized during the interval between phrenic bursts (decrementing E or post-I neurons) and those exhibiting a plateau or bell-shaped membrane potential trajectory throughout expiration (E-all neurons). Axonal projections of these medullary neurons were identified in the cranial nerves (n = 34), or in the spinal cord (n = 19) as revealed by antidromic stimulation and/or by reconstruction following horseradish peroxidase (HRP) labeling. The other 108 neurons were not antidromically activated (NAA) by the stimulations tested, or had their axons terminating inside the medulla as revealed by HRP labeling. All these respiratory neurons, except for 3 which were hypoglossal motoneurons, had their somata within the ventrolateral medulla, in the region of the nucleus ambiguus, homologous to the ventral respiratory group (VRG) of the cat. No dorsal respiratory group (DRG) was detected within the medulla of the rats. Due to this absence of a DRG, it is concluded that the neural organization of respiratory centers is quite different in cats and rats.     

Effects of amino acids on the excitability of respiratory bulbospinal neurons in solitary and para-ambigual regions of medulla in cat

The effects of inhibitory (gamma-aminobutyric acid (GABA) and glycine) and excitatory (L-glutamate and DL-homocysteate, DLH) amino acids on the excitability of respiratory bulbospinal neurons were studied in decerebrate, paralyzed, bilaterally vagotomized, artificially ventilated cats. Unit activities were recorded extracellularly in the medulla in both the ventrolateral portion of the nucleus tractus solitarius and the para-ambigual region in the vicinity of the nucleus ambiguus (dorsal and ventral respiratory groups, respectively). All neurons were bulbospinal since they could be antidromically activated by electrical stimuli to the spinal cord. We used variations in antidromic latency (ADL) as a measure of changes in excitability of the soma. All neurons exhibited variations in ADL related to the respiratory cycle, being shortest (minimum ADL) during neural activity and longest (maximum ADL) in the silent period. Neurons whose discharge frequencies fell during application of putative inhibitory amino acids showed an increase of minimum ADL compared to control, indicating hyperpolarization. Minimum ADL, in some cells, became shorter during application of excitatory amino acids, indicating depolarization; in others, mechanisms secondary to increased neuronal firing likely obscured their effects. The transient maximum ADL usually present at the onset of the silent period was increased by excitatory amino acids and, in some units, was reduced or eliminated by inhibitory amino acids. These effects are discussed in terms of a modulation by synaptic inputs and neurotransmitters of the cumulative afterhyperpolarization which follows bursts of action potentials.     

大鼠食管颈段神经形态的组化研究

本文采用多种组化方法结合神经银染技术,对大鼠的食管颈段神经形态观察发现:延髓内双侧疑核的咀侧端及迷走神经背核闩平而附近,分别见散在的多极和梭形标记细胞;颈前、中节、颈胸节和胸交感节(T_2-T_4),结状节,脊神经节(C_2-C_8)内均见标记细胞。 食管壁内的神经束及分支,由粗、细两类神经纤维组成。其中AchE阳性的胆碱能纤维占优势,分别见于外膜丛、肌内丛、粘膜下丛,腺体血管周围和粘膜肌内,粗纤维末梢伸向上皮基部和上皮之间,肌内的神经末梢呈结状膨大。外膜和肌肉见有神经节和散在的神经细胞。而食管壁内肾上腺素能纤维稀少,仅见于神经束和分支内及血管壁周围。     

Catecholaminergic neurons in the brain-stem and sleep apnea in SIDS victims

Background: Tyrosine hydroxylase (TH) is a specific marker for catecholaminergic neurones. Some reports have demonstrated a decrease of TH in the sudden infant death syndrome (SIDS) compared with controls. To further investigate this, the correlation between TH and sleep apnea was investigated here. Materials and methods: Among 27,000 infants studied prospectively to characterize their sleep–wake behavior, 38 infants died under 6 months of age. They included 26 cases of SIDS. All the infants had been recorded during one night in a pediatric sleep laboratory some 3–12 weeks before death. The frequency and the duration of sleep apnea were analyzed. The brain-stem material was collected and subjected to immunohistochemical studies for TH. The density of TH-immunoreactive neurons was measured in the nucleus hypoglossus, nervus vagus dorsalis, solitary and ambiguus and the ventrolateral medulla (VLM) in the medulla oblongata. Correlation analyses were carried out between the density of TH-immunoreactive neurons and the data from the sleep apnea studies. Results: There was no SIDS specific correlation between TH-immunoreactive neurons in the nucleus hypoglossus, nervus vagus dorsalis, solitary and ambiguus and the ventrolateral medulla in the medulla oblongata and the frequency and duration of sleep apnea. Conclusions: No significant association between the pathological data and the physiological data refers to TH-positive neurons in the medulla oblongata in SIDS victims.     

Recommendations for the reporting of tumors of the adrenal cortex and medulla

The Association of Directors of Anatomic and Surgical Pathology has developed recommendations for the surgical pathology report for common malignant tumors. The recommendations for tumors of the adrenal cortex and medulla are reported herein. Received: 30 March 1999 / Accepted: 30 March 1999     

Anoxic disturbance of the isolated respiratory network of neonatal rats

Tissue oxygen (PO₂), K⁺ (aK_e), pH (pH_e) and Ca²⁺ ([Ca²⁺]_e) were measured in the region of the ventral respiratory group (VRG) in the in vitro brainstem-spinal cord preparation of neonatal rats. During tissue anoxia, elicited by superfusion of N₂-gassed solutions, an initial increase in the frequency of respiratory activity, lasting between 2 and 12 min, turned into a frequency depression. During anoxia periods of up to 60 min, respiratory activity persisted in solutions containing CO₂/bicarbonate, whereas a complete blockade was observed after 15–25 min in N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid- (Hepes)-buffered salines. After such anoxic apnea, respiratory rhythmicity could be reactivated by superfusion of hypoxic, CO₂/bicarbonate-buffered solutions. In both types of hypoxic solutions, aK_e increased by maximally 1.5mM, whereas an initial increase of pH_e by up to 0.05 pH units turned, after 2–4 min, into an acidification which could exceed 0.5 pH units. In contrast, [Ca²⁺]_e remained unaffected by anoxia. Addition of 2–5 mM cyanide (CN^-) to oxygenated Hepes-buffered saline evoked an increase in PO₂ in the VRG from 100 to more than 300 mmHg. The effects of CN^- on respiratory activity, aK_e and pH_e were almost identical to those during anoxia. In oxygenated, CO₂/bicarbonatefree solutions of different pH, however, an increase in pH_e in the VRG led to a decrease in respiratory frequency, whereas a fall of pH_e produced a frequency acceleration. A rise of aK_e in the VRG by more than 2 mM as induced by superfusion of a 7 mM K⁺ solution led to a sustained increase of respiratory frequency. The results indicate that blockade of aerobic metabolism does not severely perturb K⁺ and Ca²⁺ homeostasis and that the biphasic response to anoxia is not directly related to the observed changes in PO₂, aK_e, pH_e, or [Ca²⁺]_e. In the respiratory network of neonatal mammals, CO₂ might provide a stimulus for long-term maintenance of respiratory activity under oxygen depletion.     

国人延髓动脉的观察

本文观察了110例成人脑标本的延髓外部动脉;采用动脉X线造影法和透明法,在20例人脑标本上观察了延髓内部动脉的形态和供应。将延髓表面分为四区,供应各区的外部动脉可分为相应的4群。前正中群和前外侧群动脉主要来自脊髓前动脉,前正中群动脉供应舌下神经核、内侧丘系及部分锥体束等中缝两侧结构;前外侧群动脉供应大部分锥体束;外侧群动脉来自椎动脉、小脑下后动脉、基底动脉和小脑下前动脉,主要供应网状结构、脊髓丘脑束、三叉神经脊束及核、迷走神经背核等;后群动脉来自脊髓后动脉和小脑下后动脉,主要供应薄、楔束核等。本文还讨论了延髓外侧区的血液供应及“终动脉”等问题。     

大鼠延髓内神经激肽B受体神经元对腹膜伤害性刺激的Fos表达——免疫组织化学双重染色研究

为探讨神经激肽Ｂ受体（ｎｅｕｒｏｋｉｎｉｎｂｒｅｃｅｐｔｏｒ，ＮＫＲ）神经元在大鼠延髓的定位及其在腹膜伤害性传入信息整合中的作用。应用免疫组织化学双重染色方法，显示ＮＫＲ神经元的分布并观察它们对腹膜化学伤害性刺激的Ｆｏｓ表达。结果表明：ＮＫＲ样免疫反应（ＮＫＲ－ＬＩ）神经元主要分布在孤束核（Ｓｏｌ）、延髓腹外侧区（ＶＬＭ）、三叉神经脊束核尾侧亚核（Ｓｐ５Ｃ）浅层和三叉旁核（Ｐａ５）。腹膜伤害性刺激激诱导的Ｆｏｓ表达神经元多数分布在Ｓｏｌ、ＶＬＭ、Ｐａ５和最后区。Ｓｏｌ、ＶＬＭ和Ｐａ５中约３０．１％的ＮＫＲ－ＬＩ神经元同时呈Ｆｏｓ样免疫反应。本研究提示：延髓内上述核团ＮＫＲ－ＬＩ神经元与腹膜伤害性初级传入信息的整合有关，可能参与内脏伤害性刺激的抗伤害性感受（ａｎｔｉ－ｎｏｃｅｃｉｐｔｉｏｎ）过程。     

大鼠延髓内含前-原脑啡肽mRNA、甲硫氨酸-脑啡肽和亮氨酸-脑啡肽神经元的分布

应用原位杂交和免疫组织化学方法,对成年大鼠延髓内含前-原脑啡肽(PPE)mRNA和甲硫氨酸-脑啡肽(M-ENK)与亮氨酸-脑啡肽(L-ENK)免疫反应神经元进行观察。结果表明:含PPEmRNA的神经元胞体,多数分布在孤束核、腹外侧区以及两者之间的网状结构等形成的一条从背内侧到腹外侧区的弧形带内。M-ENK与L-ENK样免疫反应阳性结构(神经元胞体、纤维和终末)也主要密集分布在该带内。本结果对ENK(M-ENK和L-ENK)参与延髓内脏功能活动的调控过程,提供了进一步的形态学证据。     

延髓损伤可能会引发局限型和广泛型急性胃粘膜出血

目的：通过动物实验，观察延髓损伤引起胃粘膜出血的表现形式和特点。方法：对１９只成年健康杂种狗，进行延髓一侧性损伤手术（１３只）和对照假损伤性手术（６只）；在损伤后，对胃粘膜表现进行胃镜的动态观察。结果：延髓损伤，可引起胃粘膜出血，而且发生率很高，达１００％；胃粘膜出血的严重程度及其预后有轻、重不同。结论：分析观察结果后认为：胃粘膜出血分可能有局限型和广泛型两个类型；延髓损伤的严重程度与胃粘膜出血的类型密切相关。