Rat Medulla Oblongata Research Articles

The anti-apoptotic effect of hydrogen sulfide attenuates injuries to the medullary respiratory centers of neonatal rats subjected to in utero cigarette smoke exposure

H2S may serve as an important neuroprotectant. The present experiments were performed to determine whether H2S could attenuate the injuries sustained by the medullary respiratory centers of neonatal rats that were subjected to cigarette smoke exposure (CS) in utero. Pregnant SD rats were divided into 4 exposure groups: control, CS, CS+NaHS (donor of H2S) and NaHS. Hypoxia decreased the burst frequencies of the hypoglossal rootlets of the medullary slices in CS neonatal rats, and NaHS offset the hypoxia-induced respiratory suppression. Nissl staining indicated that NaHS alleviated the injuries that were sustained by neurons after CS in utero. NaHS also decreased the number of TUNEL-positive neurons and the expression of activated caspase-3 protein in the medulla oblongata of CS neonatal rats. Furthermore, NaHS promoted Bcl-2 protein expression and reduced Bax protein and mRNA expression in the medulla oblongata of CS neonatal rats. Therefore, the present study indicates that the anti-apoptotic effect of H2S protects rat medullary respiratory centers from injuries that would otherwise be sustained from in utero CS exposure.

Site-specific hydrogen sulfide-mediated central regulation of respiratory rhythm in medullary slices of neonatal rats

Hydrogen sulfide (H2S) is involved in central regulation of respiratory rhythm at the level of the medulla oblongata. The present study was carried out to test our hypothesis that H2S exerts site-specific regulatory action on respiratory rhythm in the medulla oblongata of neonatal rats. The rhythmic discharge of hypoglossal rootlets in medullary slices of neonatal rats was recorded. 200μM NaHS (an H2S donor) increased burst frequency (BF) in 900-μm slices containing the pre-Bötzinger complex (preBötC), whereas it caused diphasic responses in 1200-, 1400- and 1800-μm slices containing both the preBötC and part or all of the parafacial respiratory group (pFRG): an initial decrease in BF followed by an increase. The initial decrease in BF was no longer observed after unilateral lesion of the pFRG region in the 1400-μm slices. In addition, BF was increased by a unilateral micro-injection of NaHS into the preBötC region, but was decreased by an injection into the pFRG region. These data support our hypothesis that the regulatory action of H2S on respiratory rhythm in the medulla oblongata is site-specific. The excitatory effect is caused by the preBötC, while the inhibitory effect is from the pFRG.

Expression of Renin–Angiotensin System Genes in Brain Structures of ISIAH Rats with Stress-Induced Arterial Hypertension

We studied the expression of genes encoding angiotensinogen (Agt), renin (Ren), angiotensin-converting enzyme (ACE), and type 1 angiotensin receptor (AT1A) in the hypothalamus and medulla oblongata of hypertensive ISIAH rats and normotensive WAG rats. The amount of Agt mRNA in the hypothalamus of young ISIAH rats was increased by 30% compared to WAG controls. In the medulla oblongata of young ISIAH rats, the levels of mRNA of Agt and AT1A receptor were enhanced by 60% and 24%, respectively, compared to WAG rats. In adult animals, the expression of the studied genes did not differ from the control. It is concluded that changes in gene expression of the renin-angiotensin system in brain structures of ISIAH rats may contribute to the development of hypertension.

Protective action of tetramethylpyrazine on the medulla oblongata in rats with chronic hypoxia

Tetramethylpyrazine (TMP), one of the active ingredients of the Chinese herb Lingusticum Wallichii Frantchat (Chuan Xiong), plays an important role in neuroprotection. However, the protective effect of TMP on the medulla oblongata, the most important region of the brain for cardiovascular and respiratory control, during chronic hypoxia remains unclear. In this study, we examined the neuroprotective effect of TMP on the medulla oblongata after chronic hypoxic injury in rats. Male Sprague-Dawley rats were randomly divided into four groups: control group, TMP group, chronic hypoxia group, and chronic hypoxia+TMP group. Rats were exposed to hypoxia (10% (v/v) O₂) or normoxia for 6 h daily for 14 days. TMP (80 mg/kg) or vehicle (saline) was injected intraperitoneally 30 min before experimentation. Loss of neurons in the pre-Bötzinger complex, the nucleus ambiguus, the nucleus tractus solitarius, the hypoglossal nucleus and the facial nucleus were evaluated by Nissl staining. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were measured, and apoptosis was monitored using the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) method. The level of Bcl-2 mRNA and Bax mRNA was quantitatively measured by RT-PCR analysis. TMP protected Nissl bodies of neurons from injury in all nuclei observed, and reduced the loss of neurons in the nucleus ambiguus, the nucleus tractus solitarius, and the hypoglossal nucleus in rats subjected to chronic hypoxia. TMP upregulated SOD activity and inhibited the increase in MDA content in the medulla oblongata of hypoxic rats. In addition, TMP decreased the rate of apoptosis index (the percentage of apoptotic cells against the total number of cells) in all medullary structures examined, excepting the nucleus ambiguus and inhibited the decrease in Bcl-2 mRNA levels in the medulla oblongata following hypoxia. Our findings indicate that TMP may protect the medullary structures that are involved in cardiovascular and respiratory control from injury induced by chronic hypoxia in rats via its anti-oxidant and anti-apoptotic effects.

Poly(amido)amine dendrimers generation 4.0 (PAMAM G4) reduce blood hyperglycaemia and restore impaired blood–brain barrier permeability in streptozotocin diabetes in rats

We hypothesized that BBB is impaired in rat model of streptozotocin-induced diabetes and can be sealed by poly(amido)amine dendrimers G4.0 (PAMAM G4), which reveal anti-glycation activity. The BBB permeabilization was monitored in rats with the 60-day streptozotocin-diabetes and non-diabetic animals, using three fluorescent dyes (given intraperitoneally) differing in molecular weight: fluorescein, fluorescein isothiocyanate (FITC)-dextran and Evans blue. All animals were administered for 2 months with either PAMAM G4 dendrimer or placebo. The fluorescence intensities of the injected fluorescent markers were recorded in the homogenates of selected brain regions. The highest accumulations of the used fluorescent dyes were observed for fluorescein, predominantly in thalamus, hippocampus, frontal cortex, striatum and cerebellum. FITC-dextran leaked to much smaller extent, however, higher permeabilization for FITC-dextran was revealed in pons-medulla oblongata, frontal and parietal cortex of diabetic compared to control animals. Evans blue leaked very slowly into striatum and pons-medulla oblongata in diabetic rats. The treatment of diabetic animals with PAMAM G4 significantly reduced blood glucose concentration and hallmarks of late diabetic complications, compared to non-treated diabetic animals. PAMAM G4 significantly reduced diabetes-induced permeabilization of BBB, which remained in line with the reduced blood glucose and the amelioration of the biochemical hallmarks of severe hyperglycaemia.

Prenatal and perinatal acrylamide disrupts the development of cerebrum and medulla oblongata in albino rats

Acrylamide is known to cause neurotoxicity in experimental animals and humans. The literature on its neurotoxic effect in adult animals is huge, but the effect of acrylamide on the embryonic and postnatal development is relatively less understood. The present study examined its effects on the development of oxidative stress of cerebrum and medulla oblongata in albino rats. Acrylamide was orally administered to non-anesthetized pregnant females by gastric intubation 10 mg/kg/day. The animals were divided into 3 groups as follows: group A - newborn from control animals, group B - newborns from mothers treated with acrylamide from day 7 (D7) of gestation till birth (prenatal intoxicated group), group C - newborns from mothers treated with acrylamide from D7 of gestation till D28 after birth (perinatally intoxicated group). Acrylamide administered either prenatally or perinatally was shown to induce significant increase of thiobarbituric acid-reactive substances (TBARS) and oxidative stress (significant reductions in glutathione (GSH), total thiols, superoxide dismutase (SOD), and peroxidase activities) in the developing cerebrum and medulla oblongata. The results of this study showed that prenatal and perinatal acrylamide or its metabolites disrupts the biochemical machinery, cause oxidative stress and induce structural changes in the developing rat cerebrum and medulla oblongata. Key words: Acrylamide, postnatal development, cerebrum, medulla oblongata, oxidative stress.

Nitric oxide synthase expression in the medullary respiratory related nuclei and its involvement in CO-mediated central respiratory effects in neonatal rats

The present study was conducted in order to observe the potential participation of the nitric oxide synthase–NO pathway in CO-mediated regulation of respiration of neonatal rats. An immunofluorescent histochemical technique was used to examine the existence of the neuronal nitric oxide synthase, a key enzyme of synthesizing NO, in medullary respiratory nuclei. The rhythmic respiratory-like discharges of hypoglossal rootlets of medullary slices were recorded to test the role of the nitric oxide synthase in CO-mediated respiratory effects. We observed neuronal nitric oxide synthase expressed in the medullary respiratory nuclei in conjunction with CO lengthened expiratory duration, decreased respiratory frequency, and increased inspiratory amplitude. These CO-mediated respiratory effects could be partially eliminated by prior treatment of the slices with Nω-nitro- l-arginine methyl ester, an inhibitor of nitric oxide synthase. The results suggest that nitric oxide synthase–NO pathway might be involved in the CO-mediated central regulation of respiration at the level of medulla oblongata in neonatal rats.

Age-related changes in nitroxidergic neurons in some nuclei of rat medulla oblongata

The paper presents a comparative study of NO neurons in the solitary tract nucleus, giant-cell, and lateral reticular nuclei in rats at 4, 7, 10, 14, 30, 45, and 60 days old and 3, 6, 12, 18, 24 months old. We determine the active quantitative and qualitative changes that occur in NO-positive neurons in the studied nuclei during the course of postnatal development. A low level of enzyme activity is observed on the first day; it reaches a peak level around the first-third month, then slowly declines. The size and number of nitroxidergic neurons increases, while the relative cell density decreases until the third month of life. We reveal local differences in the ontogenetic development of NO neurons in the studied nuclei. Solitary tract neurons have the highest rate of development, while NO neurons of old animals undergo early and extreme changes as compared to other studied nuclei of rat medulla oblongata.

Direct in vivo measurement of glycine and the neurochemical profile in the rat medulla oblongata

The medulla oblongata (MO) contains a high density of glycinergic synapses and a particularly high concentration of glycine. The aims of this study were to measure directly in vivo the neurochemical profile, including glycine, in MO using a spin-echo-based (1)H MRS sequence at TE = 2.8 ms and to compare it with three other brain regions (cortex, striatum and hippocampus) in the rat. Glycine was quantified in MO at TE = 2.8 ms with a Cramér-Rao lower bound (CRLB) of approximately 5%. As a result of the relatively low level of glycine in the other three regions, the measurement of glycine was performed at TE = 20 ms, which provides a favorable J-modulation of overlapping myo-inositol resonance. The other 14 metabolites composing the neurochemical profile were quantified in vivo in MO with CRLBs below 25%. Absolute concentrations of metabolites in MO, such as glutamate, glutamine, γ-aminobutyrate, taurine and glycine, were in the range of previous in vitro quantifications in tissue extracts. Compared with the other regions, MO had a three-fold higher glycine concentration, and was characterised by reduced (p < 0.001) concentrations of glutamate (-50 ± 4%), glutamine (-54 ± 3%) and taurine (-78 ± 3%). This study suggests that the functional specialisation of distinct brain regions is reflected in the neurochemical profile.

Nitroxidergic neurons in nuclei of rat and human medulla oblongata

Four types of neurons distinguished by NADPH-diaphorase reaction have been identified in seven nuclei of human and rat medulla oblongata. It was found that nitrogen oxide (NO)-positive neurons had similar distributions; neurons with high NO-synthase activity predominated in vasomotor nuclei and, in sensitive nuclei, most neurons had low NO-syntase activity.

Nitroxidergic Neurons in Nuclei of the Medulla Oblongata in Hypertensive and Normotensive Rats

Distribution of nitroxidergic neurons and neuronal NO-synthase activity in certain medulla oblongata nuclei were studied in normotensive and hypertensive rats with different types of arterial hypertension. In rats with renovascular hypertension, neuronal NO-synthase activity markedly decreased in most nuclei 2 weeks after surgery, while the number of NO-positive cells did not change significantly; after 4 weeks, the percentage of NO-positive neuron markedly decreased and neuronal NO-synthase activity also slightly decreased. No further decrease in neuronal NO-synthase activity was observed 8 week after intervention, but the percentage of NO-neurons decreased compared to that in normotensive rats. In spontaneously hypertensive rats, changes in most nuclei were directed similarly to those observed in 8-week renovascular hypertension, but motor nuclei demonstrated less differentiated reaction to hypertension. In all cases, changes in the parameters observed in sensory nucleus (n. solitarius) appeared earlier and were more pronounced than in nuclei of the reticular formation related to bulbar vasomotor center.

Norepinephrine Content in the Hypothalamus and Medulla Oblongata of ISIAH Rats is Regulated by Several Genetic Loci

Five genetic loci regulating epinephrine content in rat hypothalamus and two loci in the medulla oblongata were identified using polymorphic microsatellite DNA markers. Allele polymorphism of these loci determines the differences between norepinephrine levels in brain compartments of hypertensive ISIAH and normotensive WAG rats. The interactions between the detected epinephrine-regulating loci are additive.

NAADP-mediated channel ‘chatter’ in neurons of the rat medulla oblongata

NAADP (nicotinic acid-adenine dinucleotide phosphate) is a potent Ca(2+)-mobilizing messenger that stimulates Ca(2+) release in a variety of cells. NAADP-sensitive Ca(2+) channels are thought to reside on acidic Ca(2+) stores and to be functionally coupled to IP(3) (inositol 1,4,5-trisphosphate) and/or ryanodine receptors located on the endoplasmic reticulum. Whether NAADP-sensitive Ca(2+) channels 'chatter' to other channels, however, is not clear. In the present study, we have used a cell-permeant NAADP analogue to probe NAADP-mediated responses in rat medulla oblongata neurons. NAADP-AM (NAADP-acetoxymethyl ester) evoked global cytosolic Ca(2+) signals in isolated neurons that were reduced in amplitude by removal of external Ca(2+), abolished by disruption of acidic compartments and substantially inhibited by blockade of ryanodine receptors. In rat medullary slices, NAADP-AM depolarized neurons from the nucleus ambiguus in the presence of intracellular EGTA, but not of the faster Ca(2+) chelator BAPTA [1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid]. Depolarization was also dependent upon extracellular Ca(2+), acidic stores and ryanodine receptors. In voltage-clamp mode, NAADP-AM induced an inward current with a reversal potential of approx. 0 mV. The results of the present study reveal the presence of acidic NAADP-sensitive Ca(2+) stores in medulla neurons, the mobilization of which results not only in global Ca(2+) signals but also in local signals that activate non-selective cation channels on the cell surface resulting in depolarization. Thus NAADP is capable of co-ordinating channels both within the cell interior and at the cell membrane representing a novel mechanism for excitation of central neurons.

Posterior lateral hypothalamic axon terminals are in contact with trigeminal premotor neurons in the parvicellular reticular formation of the rat medulla oblongata

This study was performed to understand the anatomical substrates of hypothalamic modulation of jaw movements. After cholera toxin B subunit (CTb) injection into the parvicellular reticular formation (RFp) of the rat medulla oblongata, where many trigeminal premotor neurons have been known to exist, numerous CTb-labeled neurons were found in the posterior lateral hypothalamus (PLH) bilaterally with a clear-cut ipsilateral dominance. After ipsilateral injections of biotinylated dextran amine (BDA) into the PLH and CTb into the motor trigeminal nucleus (Vm), the prominent distribution of BDA-labeled axon terminals around CTb-labeled neurons was found in the RFp region just ventral to the nucleus of the solitary tract and medial to the spinal trigeminal nucleus ipsilateral to the injection sites. Within the neuropil of the RFp, BDA-labeled axon terminals made an asymmetrical synaptic contact predominantly with dendrites and additionally with somata of the RFp neurons, some of which were labeled with CTb. It was further revealed that these BDA-labeled axon terminals were immunoreactive for vesicular glutamate transporter 2. The present data suggest that the PLH plays an important role in the control of jaw movements by exerting its glutamatergic excitatory action upon RFp neurons presynaptic to trigeminal motoneurons.

Effects of treadmill running exercise on neuronal expression of c-Fos protein in the medulla oblongata after unilateral phrenicotomy in Wistar rats

The purpose of this study was to examine whether treadmill running exercise after phrenicotomy resulted in change in neuronal expression of c-Fos protein in the medulla oblongata in Wistar rats. All rats were subjected to left-sided unilateral phrenicotomy. In test experiments, rats were trained with treadmill running for 4 weeks, while in control experiments rats were not provided with the opportunity to exercise. c-Fos protein, a transient transcription factor, was immunohistochemically stained by the ABC method, and surveyed in the medulla oblongata. Numbers of c-Fos-immunoreactive (c-Fos-ir) neurons were counted microscopically, and their distribution in the medulla oblongata was mapped. In the dorsal respiratory group (DRG), numbers of c-Fos-ir neurons were found to be significantly increased in the test rats compared with control rats, while in the ventral respiratory group (VRG) no significant differences were found in numbers of c-Fos-ir neurons between test and control rats. These findings suggest that DRG neurons may play more important roles than VRG neurons in recovery of respiration in treadmill exercise after unilateral phrenicotomy in Wistar rats.

Ultrastructural changes in the lateral reticular nucleus of the medulla oblongata in prepubertal rats under the effect of long-term stress exposure

Ultrastructural changes in the lateral reticular nuclei of the medulla oblongata of rat pups developing under the effect of chronic mental and pain stress indicate impaired histogenesis of structures of the medulla oblongata reticular formation and appearance of pronounced morphofunctional differences between the neurons.

Expression and localisation of somatostatin receptor subtypes sst1–sst5 in areas of the rat medulla oblongata involved in autonomic regulation

Somatostatin is known to modulate the activity of neurones of the medulla oblongata involved in autonomic regulation, mediated through five subtypes of G protein-coupled receptors, sst1–sst5. This study utilises reverse transcription polymerase chain reaction and immunohistochemistry to investigate the expression of sst1–sst5, including the sst2 A/sst2 B isoforms, in the main autonomic centres of the rat medulla oblongata: nucleus of the solitary tract (NTS), dorsal motor vagal nucleus (DVN) and ventrolateral medulla (VLM). In tissue from the cerebral cortex, hippocampus and cerebellum all subtype mRNAs were detected, but sst5 signals were weak, and the distribution of sst1–sst5 immunoreactivities was consistent with previous reports. In the medulla, all sst mRNAs gave clear amplicons and subtype-specific antibodies produced characteristic patterns of immunolabelling, frequently in areas of somatostatinergic innervation. Anti-sst1 labelled beaded fibres, sst2 A, sst2 B, sst4 and sst5 gave somatodendritic labelling and sst3 labelled presumptive neuronal cilia. In NTS tissue, sst1, sst2 A, sst4 and sst5 mRNAs were strongly expressed, while in VLM tissue sst1, sst2 A, sst2 B and sst4 predominated. In both areas of the medulla, neurones with intense somatodendritic sst2 A immunoreactivity were principally catecholaminergic in phenotype, being double labelled for tyrosine hydroxylase (TH) and phenylethanolamine- N-methyl-transferase (PNMT). Some TH/PNMT positive neurones were also sst2 B and sst4 immunoreactive. Cholinergic parasympathetic neurones in the DVN were immunoreactive for the sst2 A, sst2 B, sst4 and sst5 subtypes. These observations are consistent with the proposal that multiple somatostatin receptor subtypes, possibly combining as heterodimers, are involved in mediating the modulatory effects of somatostatin on autonomic function, including cardiovascular, respiratory and gastrointestinal reflex activity.

DITTMAR AND THE HISTORY OF STEREOTAXY; OR RATS, RABBITS, AND REFERENCES

The renaissance of stereotactic functional neurosurgery has resulted in increased interest in its origins. Twenty articles concerning this field trace the history back to a paper published in 1873 by Dittmar: "Uber die Lage des sogenannten Gefaesszentrums in der Medulla oblongata" [On the location of the so-called vasomotor center in the medulla oblongata]. Few facts are presented. But, taken together, the impression given by the secondary sources is that Dittmar, in 1873, presented a guiding device for localization of intracranial structures for the positioning of electrodes/blades in the medulla oblongata in rats. Of the publications that cite Dittmar's original article as their only quoted source, half did not specify the inserted object and the animal of the experiment. The remaining articles reported either that the introduced object was an electrode or that the experiments were performed on rats. Dittmar's original article, however, did not report use of his apparatus for insertion of electrodes, nor did he use rats. All experiments were performed by making incisions in the medulla oblongata in rabbits. Dittmar's apparatus was constructed to allow more precision when performing incisions in the medulla oblongata than could be obtained performing incisions freehand. The incision point was chosen and the blade introduced with direct visual guidance. This has been described as "spatial localization of intracranial structures," "a special targeting instrument," or simply, "a guiding device." In our opinion, it can most properly be classified as a supportive arm.

Effects of CO 2 inhalation on 5-HT release in the dorsomedial medulla oblongata in infant rats

Effects of CO 2 inhalation on 5-HT release in the dorsomedial medulla oblongata in infant rats

Neurokinin 1 receptor plastically changes excitability of neurons in reticular formation of rat medulla oblongata

Neurokinin 1 receptor plastically changes excitability of neurons in reticular formation of rat medulla oblongata