The pressor zone in the caudal part of the ventral surface of the medulla oblongata

The changes of the vessel resistance of the skeletal muscle and the small intestine perfused with constant blood flow, under electrical stimulation of the ventrolateral medulla were studied on artificially ventilated urethane-anesthetized cats. The stimulation of rostral ventrolateral medulla increased vessel resistance in both regions. The stimulation in a region 2 mm caudal the middle of the rootlets of the twelfth cranial nerves decreased the vessel resistance, but in a region 4 mm caudal the middle of the same rootlets increased the vessel resistance of the skeletal muscle and the small intestine.     

Changes in gas composition of expired air during electric stimulation of the ventral medulla oblongata]

The experiments on urethane-anesthetized cats with the electrically stimulated ventral brain stem revealed that caudal ventral medulla at the depth of 1500 microns possesses structures whose electrical activation increases the level of carbon dioxide in arterial blood and in the end portion of expirate, on the one hand, and decreases the oxygen content in expirate and arterial blood, on the other hand.     

大鼠延髓尾端加压区微量注射L—精氨酸对血压、心率和肾灌流压的影响

目的：研究NO前体L-Arg微量注入大鼠延髓尾端加压区（CPA）对心血管活动的影响。并探讨其可能的机制。方法：采用延髓腹外侧部微量满面主射法,以整体灌流肾为模型观察与NO代谢有关的试剂对心血管活动的影响。结果：（1）CPA内微量注入L-Arg(60-100nmodl)。动脉血压与心率呈剂量依赖性下降,肾灌流压下降,与生理盐水对照,差异有显著意义;（2）预先在CPA内注入鸟苷酸环化酶抑制剂甲基蓝可取消L-Arg的降压降肾灌流压作用;（3）CPA内注入lu,AP上升,如预先注入L-Arg后5min再注入L-Glu,L-Glu的升压效应被衰减,期衰减程度与L-Arg是剂量依赖性关系。结论：CPA内的L-Arg-NO通路参与延髓心血管中枢对AP的调控,其机制之一可能是通过cGMP抑制CPA内谷氨酸能神经突触。     

Oxytocinergic exohypothalamic connections to the medulla oblongata in the pigeon and rat

The neurosecretory hypothalamo-hindbrain connection of lower vertebrates is also present in the pigeon and the rat. By means of the immunohistochemical technique and the pseudoisocyanine technique these fibres could be seen following known pathways through the mesencephalic reticular formation to the hindbrain. Here the fibres enter the region of the dorsal columns nuclei. The neurophysine vesicles demonstrable electronmicroscopically in these fibres are identical with the well known neurophysine vesicles which are present in the neurohypophysis of the investigated species. The content of the vesicles is indeed neurophysine as proved with the method by NAUMANN and STERBA [1]. The terminals of the fibres form neuro-neuronal synapses.     

大鼠延髓腹面降压区微量注射L—精氨酸对心血管活动的影响

目的：观察NO前体L－精氨酸（L－Arg)微量注入大鼠延髓腹面降压区（VSMd）对心血管活动的影响及其和L－谷氨酸（L－Glu)降压作用的关系。方法：采用延髓腹外侧部微量注射法,以整体灌流肾为模型观察与NO有关的药物对心血管活动的影响。结果：①VSMd内微量注入L－Arg,动脉血压（AP）呈剂量依赖性升高,肾灌流压（PPK）与AP同步上升,与注入生理盐水对照,差异均具有显著意义,但L－Arg对心率无显著影响;②预先在VSMd内注入甲基蓝可取消L－Arg的升压、升PPK作用;③VSMd内注入L－Glu,AP下降。如预先注入L－Arg后5min再注入L－Glu,L-Glu的降压效应被衰减,其衰减程度依赖于L－Arg剂量。结论：VSMd的L－Arg-NO通路参与延髓心血管中枢对AP的调控,其机制之一可能是通过cGMP抑制VSMd内的谷氨酸能神经突触。     

大鼠延髓尾端加压区对外周血管紧张的影响

本文以血管的灌流压变化反映血管紧张性,观察Ｌ－谷氨酸及肾上腺素能受体阻断剂微量注射于大鼠延髓腹面心血管活动调控区对骨骼肌血管和肾血管紧张的影响。实验观察到,Ｌ－－ｇｌｕ兴奋延髓尾端加压区（ＣＰＡ）在动脉直升的同时,双后肢骨骼肌灌流压上升３７．５９％,左肾灌流压上升１７．０４％,如预先在延髓腹面加我注入普萘少尔或酚妥拉明均能明显减小Ｌ－ｇｌｕ兴奋ＣＰＡ时的灌流压和肾灌流压升高效应。提示ＣＰＡ对外周血     

Neurons of the medulla oblongata and hypothalamus projecting on the sympathetic neurons of the ventral horn of the spinal cord]

Connections of the neurons of the spinal cord ventral horn with the structures, situating above have been investigated. After injection of uranyl acetate into the TIII segment of the spinal cord, labelled neurons are found in various reticular nuclei of the medulla oblongata. At the level of the roots of the XII pair of the cranial nerves they are revealed in the reticular paramedian, ventral, parvocellular and lateral nuclei. The formations mentioned participate in regulation of the cardio-vascular system. More rostral (2 and 4 mm relatively to the roots of the XII pair of the cranial nerves) the neurons are observed in the reticular giant cellular nucleus, in nuclei of the raphe and in the group of the P-substance reactive neurons. Besides, labelled neurons are revealed in the posterior, lateral fields and in the dorso- and ventromedial nuclei of the hypothalamus.     

Light and electronmicroscopic study of area M, the chemosensitive area of the ventral medulla oblongata

An electron and light microscopic study was performed to elucidate the structure of area M, an area on the ventral surface of the medulla oblongata which participates in the central respiratory control of the cat. We found no particular morphological barriers to fluid transport from the cerebrospinal fluid space towards the capillaries of this area. The astroglial contacts proved to be mostly gap junctions; furthermore, no tight junctions could be found here. Multipolar ganglion cells could be localized at a depth of 400-800 micron. These cells form numerous synaptic contacts with thin, unmyelinated axons running superficially, parallel to the pial surface in area M. Our findings support the contention that the ventral chemosensitive areas of the medulla oblongata are influenced by the chemical constitution of the cerebrospinal fluid.     

Effect of structures of the ventral surface of the medulla oblongata on coupled vascular functions of the small intestine

The effect of the ventrolateral medulla electrical stimulation of various intensity on resistance, capacitance and exchange functions was studied in the vascular bed of the small intestine. Brain activation with superliminal current applied to a point 2 mm rostral-wise of the middle of the twelfth cranial nerve rootlets has been shown to produce the strongest effect on the precapillary resistance of the vascular bed, whereas brain stimulation in a point 2 mm caudal-wise of this level produces a much stronger effect on the postcapillary small intestine resistance.     

The capacitive function of the spleen during electrical stimulation of the structures of the ventral section of the medulla oblongata

In acute experiments on cats under perfusion with constant blood expenditure of hemodynamically isolated spleen the authors studied the reactions of its vessels in the electrical stimulation of ventral brainstem. It was shown that the stimulation of the rostral zone of these structures increased vein outflow from the spleen. It was shown the deterioration of the parametres which characterize a capacitance function of the spleen by stimulation of a causal depressor zone of the brainstem by means of the current of threshold size and its increase by irritation of the brain structures with a 2 threshold current size. There have been made a supposition has been made about the participation of the pointed structures of the brain in the regulation of a vasomotion tonus of the spleen vessels.     

Study of cardio- and hemodynamic reactions to administration of GABA into the neuronal structures of the ventrolateral area of the medulla oblongata of cats

The data obtained in acute experiments on cats have indicated that the most GABA-sensitive injected neuronal structures in the ventrolateral medulla appear to be located in the vicinity to the roots of the XII cranial nerves. GABA injected into these structures just rostrally to the roots induced hypotensive reactions due to heart rate and myocardial contractile activity decrease, besides inhibition of sympathetic vasoconstrictor influences. GABA injected into the neuronal structures in the caudal ventrolateral medulla induced hypertensive reactions, to a large extent due to increase in heart rate and contractile activity of myocardium.     

Immunohistochemical demonstration of c-fos protein in neurons of the medulla oblongata of the musk shrew (Suncus murinus) after veratrine administration.

We subcutaneously injected 0.5 mg/kg veratrine into the musk shrew (Suncus murinus), observed the presence or absence, latency, and the incidence of vomiting in each animal for 90 min, and selected animals that frequently vomited (FV group) and those that did not vomit (NV group). Subsequently, animal brains were removed, and the induction of c-fos protein (Fos) was immunohistochemically examined to evaluate neuronal activity in the medulla oblongata. The distribution of Fos-positive neurons in the medulla oblongata was similar between FV and NV groups, with numerous neurons along the entire length of the nucleus of the solitary tract and in the ventrolateral reticular formation. Both veratrine-injected groups showed higher numbers of positive neurons than the saline administered group. However, while the FV group showed a high concentration of positive neurons in the dorsal-dorsomedial reticular formation of the nucleus ambiguus in the rostral medulla, the NV group showed few positive neurons in this area. Fos activity in neurons in this area appeared to be higher in animals with a higher incidence of vomiting.     

Development of catecholaminergic neurons in the human medulla oblongata

Distribution and maturation of catecholaminergic (CA) neurons have been studied by tyrosine hydroxylase immunohistochemistry in the medulla oblongata of human fetuses aged 14.5-25 weeks of gestation. Already at 14.5 weeks, CA neurons were observed in two longitudinally oriented cell clusters, one located ventrolaterally in the area of the lateral reticular and ambiguous nuclei, the other one dorsomedially forming 4 groups related to the dorsal vagal nucleus, the commissural nucleus of the vagus, the nucleus of the tractus solitarius and the area postrema. CA neurons in the area postrema were often found close to blood vessels. Scattered intermediate CA neurons were seen between these two larger clusters. CA neurons still appeared immature exhibiting bipolar morphology with only one or two short stout processes, which hardly branched. At 21 weeks, CA neurons occupied essentially the same location, but had a more mature morphology. Though still bipolar in shape, they had thinner and much longer processes which frequently branched. Both in the ventrolateral and the dorsomedial cell clusters, these processes were frequently lying close to blood vessels. At 25 weeks, CA cells had matured into multipolar neurons with long thin processes forming fine fiber networks in the ventrolateral medulla as well as around and within the dorsal vagal and solitarius nuclei. Only at this stage, a distinct CA fiber tract was seen located in the region of the tractus solitarius. Our results indicate that CA neurons in the human medulla, which are presumably involved in the control of ventilation and blood pressure, though generated rather early during development, mature relatively late.     

Immunohistochemical mapping of adrenomedullin in the human medulla oblongata

We studied by immunocytochemistry the expression of adrenomedullin (AM) in the human medulla oblongata, sampled from 13 adult subjects (mean age: 38 years), whose medical history was negative for neurological and neurovascular pathologies. Immunoreactive neurons were found in the medulla oblongata with statistically significant differences among the various nuclei (one-way ANOVA, P < 0.001). The hypoglossal nucleus showed higher AM expression than that of the spinal tract of the trigeminal nerve (P < 0.05), solitary tract nucleus (P < 0.05), nucleus intercalatus (P < 0.05), and area postrema (P < 0.05). The arcuate nucleus and inferior olivary nuclear complex showed lower AM expression than the hypoglossal nucleus (P < 0.001), vestibular nuclei (P < 0.01), cuneate and gracile nuclei (P < 0.05), lateral column of the reticular formation (P < 0.05), and nucleus ambiguous (P < 0.05). Furthermore the nuclei were grouped with reference to their function, into somatic sensitive nuclei, somatic motor nuclei, visceral nuclei, reticular formation, and nuclei involved in cerebellar functions. The ANOVA revealed statistically significant differences (P < 0.001) in mean AM scores among the different groups. Nuclei involved in cerebellar function showed the lowest mean AM score (P < 0.05). The difference in AM score between somatic motor nuclei and visceral nuclei was also statistically significant (P < 0.05). Widespread AM immunoreactivity in the nuclei of the medulla oblongata may account for the role of the peptide in neuronal function and regulation of regional blood flow. Differences in the expression of AM in the nuclei studied indicate the different involvement of AM in neurotransmission and neuromodulation.