Rat Medulla Oblongata Research Articles

Study on the involvement of microglial S100A8 in neuroinflammation and microglia activation during migraine attacks

BackgroundMicroglia is the primary source of inflammatory factors during migraine attacks. This study aims to investigate the role of microglia related genes (MRGs) in migraine attacks. MethodsThe RNA sequencing results of migraineurs and the panglaodb database were used to obtain differentially expressed genes (DEGs) in migraine related to microglia. A migraine rat model was established for validating and localizing of the MRGs, and subsequent screening for target genes was conducted. A shRNA was designed to interference the expression of target genes and administered into the trigeminal ganglion (TG) of rats. Pain sensitivity in rats was evaluated via the hot water tail-flick (HWTF) and formalin-induced pain (FIP) experiments. ELISA was used to quantify the levels of inflammatory cytokines and CGRP. WB and immunofluorescence assays were applied to detect the activation of microglia. ResultsA total of five DEGs in migraine related to microglia were obtained from RNA sequencing and panglaodb database. Animal experiments showed that these genes expression were heightened in the TG and medulla oblongata (MO) of migraine rats. The gene S100A8 co-localized with microglia in both TG and MO. The HWTF and FIP experiments demonstrated that interference with S100A8 alleviated the sense of pain in migraine rats. Moreover, the levels of TNFα, IL-1β, IL-6, and CGRP in the TG and MO of rats in the model rats were increased, and the expression of microglia markers IBA-1, M1 polarization markers CD86 and iNOS was upregulated. Significantly, interference with S100A8 reversed these indicators. ConclusionInterference with S100A8 in microglia increased the pain threshold during migraine attacks, and inhibited neuroinflammation and microglia activation.

A comparative assessment of age-related nicotinamide adenine dinucleotide phosphate-diaphorase positivity in the spinal cord and medulla oblongata of pigeons, rats, and mice.

Nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase (N-d) positive neurons have been extensively studied across various animals, and N-d neurodegenerative neurites have been detected in some aged animal models. However, detailed knowledge on N-d positivity and aging-related alterations in the spinal cord and medulla oblongata of pigeons is limited. In this study, we investigated N-d positivity and age-related changes in the pigeon's spinal cord and medulla oblongata and compared them to those in rats and mice. Pigeons, had more N-d neurons in the dorsal horn, around the central canal, and in the column of Terni in the thoracic and lumbar segments, with scattered neurons found in the ventral horn of the spinal segments. N-d neurons were also present in the white matter of the spinal cord. Morphometric analysis revealed that the size of N-d soma in the lumbosacral, cervical, and thoracic regions was substantially altered in aged pigeons compared to young birds. Furthermore, the lumbar to sacral segments underwent significant morphological alterations. The main findings of this study were the presence of age-related N-d positive bodies (ANB) in aged pigeons, predominantly in the external cuneate nucleus (CuE) and occasionally in the gracilis and CuEs. ANBs were also identified in the gracile nuclei and spinal cord in the aged rats and mice, whereas in aged rats, ANBs were detected in the CuE spinal nucleus. Immunohistochemistry showed that the age-related alterations occurred in the cell types and neuropeptides in old animals. The results suggest weak inflammatory response and neuronal dysfunction in the spinal cord in aged pigeons. Our results suggested that the ANB could be a potential aging marker for the central nervous system.

α7nAChR-mediated astrocytic activation: A novel mechanism of Xiongzhi Dilong decoction in ameliorating chronic migraine

Ethnopharmacological relevanceAlpha 7 nicotinic acetylcholine receptor (α7nAChR)-mediated astrocytic activation is closely related to central sensitization of chronic migraine (CM). Xiongzhi Dilong decoction (XZDL), originated from Xiongzhi Shigao decoction of Yi-zong-jin-jian, has been confirmed to relieve CM in experiment and clinic. However, its underlying mechanism for treating CM has not been elucidated. Aim of the studyTo reveal the underlying mechanisms of XZDL to alleviate CM in vivo focusing mainly on α7nAChR-mediated astrocytic activation and central sensitization in TNC. Materials and methodsCM rat model was established by subcutaneous injection of nitroglycerin (NTG) recurrently, and treated with XZDL simultaneously. Migraine-like behaviors of rats (ear redness, head scratching, and cage climbing) and pain-related reactions (mechanical hind-paw withdrawal threshold) of rats were evaluated before and after NTG injection and XZDL administration at different points in time for nine days. The immunofluorescence single and double staining were applied to detect the levels of CGRP, c-Fos, GFAP and α7nAChR in NTG-induced CM rats. ELISA kits were employed to quantify levels of TNF-α, IL-1β, and IL-6 in medulla oblongata of CM rats. The expression levels of target proteins were examined using western blotting. Finally, methyllycaconitine citrate (MLA, a specific antagonist of α7nAChR) was applied to further validate the mechanisms of XZDL in vivo. ResultsXZDL significantly attenuated the pain-related behaviors of the NTG-induced CM rats, manifesting as constraints of aberrant migraine-like behaviors including elongated latency of ear redness and decreased numbers of head scratching and cage climbing, and increment of mechanical withdrawal threshold. Moreover, XZDL markedly lowered levels of CGRP and c-Fos, as well as inflammatory cytokines (IL-1β, IL-6 and TNF-α) in CM rats. Furthermore, XZDL significantly enhanced α7nAChR expression and its co-localization with GFAP, while markedly inhibited the expression of GFAP and the activation of JAK2/STAT3/NF-κB pathway in the TNC of CM rats. Finally, blocking α7nAChR with MLA reversed the effects of XZDL on astrocytic activation, central sensitization, and the pain-related behaviors in vivo. ConclusionXZDL inhibited astrocytic activation and central sensitization in NTG-induced CM rats by facilitating α7nAChR expression and suppressing JAK2/STAT3/NF-κB pathway, implying that the regulation of α7nAChR-mediated astrocytic activation represents a novel mechanism of XZDL for relieving CM.

Analysis of the relationship between the activity of the reticular formation of the medulla oblongata, respiratory and cardiovascular systems in rats under painful stimulation

Using the method for calculating the average of conditional probabilities of recurrence intervals, a comparative analysis was performed to estimate the direction of coupling between different physiological rhythms in the form of fluctuations in blood pressure, respiration, and the activity of neurons in the reticular formation of the medulla oblongata in two groups of anesthetized rats under pain stimulation or no stimulus. It was found that there are different kinds of the directions of coupling between the analyzed rhythms. Most of the data obtained for rats from the control group and rats with experimentally induced colitis suggest the statistically significant unidirectionality of coupling. Painful stimulation did not affect the direction of coupling, but the amount of data on unidirectionaity of coupling slightly reduced. At the same time, the rhythms associated with the cardiovascular system (blood pressure variability) were controlled by the rhythms of the respiratory system, and the respiratory rhythm controlled the variability of the activity of neurons in the reticular formation of the medulla oblongata.

C-Fos Expression in Rat Medulla Oblongata after Subdiaphragmatic Vagotomy and Various Antigens Administration

c-Fos Expression in Rat Medulla Oblongata after Subdiaphragmatic Vagotomy and Various Antigens Administration

Study of the Mechanism of Antiemetic Effect of Lavandula angustifolia Mill. Essential Oil Based on Ca2+/CaMKII/ERK1/2 Pathway.

PurposeTo investigate the effective components and possible mechanism of action of Lavandula angustifolia Mill. essential oil (LEO) in preventing vomiting through the olfactory pathway.Materials and MethodsA new network pharmacology–based method was established to analyze main components and pathways of LEO involved in antiemetic effects by introducing component content; biological activities of key proteins of the olfactory pathway and their corresponding compounds were verified by molecular docking technique; and finally pica in a rat model was established to verify the molecular mechanism of antiemetic effects of LEO by enzyme-linked immunosorbent assay (ELISA) to determine the serum 5-HT, substance P, and DA levels in each group and by immunohistochemistry to determine the contents of 5-HT3R, CaMKII and ERK1/2 proteins in the medulla oblongata tissue.ResultsNetwork pharmacology combined with molecular docking analysis showed that the mechanism of the antiemetic effect of LEO may be related to (2Z)-3,7-dimethyl-2,6-octadienyl acetate, linalyl acetate, butanoic acid, hexyl ester, 4-hexen-1-ol, 5-methyl-2-(1-methylethenyl)-, acetate, .tau.-cadinol and other active ingredients, which regulate the cyclic adenosine monophosphate (cAMP) signaling pathway and the expression of BRAF, PDE and other targets on the pathway. An ELISA revealed that LEO reduced the levels of 5-hydroxytryptamine (5-HT), substance P, and dopamine in serum compared with the model group (P <0.05). Immunohistochemical analysis showed that LEO decreased the expression of 5-HT3R, CaMKII, and ERK1/2 proteins in the medulla oblongata of rats compared with the model group (P <0.01).ConclusionLEO may achieve the antiemetic effect by reducing the content of 5-HT and inhibiting its related receptors, thereby regulating downstream Ca2+/CaMKII/ERK1/2 pathway of the cAMP signaling pathway.

Does the Operation of Mitochondrial ATP-Dependent Potassium Channels Affect the Structural Component of Mitochondrial and Endothelial Dysfunctions in Experimental Parkinsonism?

We have previously demonstrated that the development of oxidative stress in some pathologies can be prevented by activation of the mitochondrial ATP-dependent potassium channel (mitoKATP). Here we studied the effect of modulation of mitoKATP on the development of mitochondrial and endothelial dysfunction in the medulla oblongata and myocardium of rats with experimental parkinsonism. It is known that uridine-5'-diphosphate, activator of mitoKATP, does not penetrate the plasma membrane, but it can be synthesized in cells from exogenous uridine that is delivered into cells by special transport systems. Our results suggest that mitoKATP is involved in the development of mitochondrial and endothelial dysfunction in experimental parkinsonism and prove the cardio- and neuroprotective effects of uridine.

Adenosine A1 and A2a receptors modulate the nitrergic system in cell culture from dorsomedial medulla oblongata.

Adenosine and nitric oxide act on the fine-tuning regulation of neural cardiovascular control in the nucleus tractus solitarius (NTS). Although the interaction between adenosine and NO is well known in the periphery, the mechanisms by which adenosine interferes in the dynamics of nitrergic neurotransmission, related to neural control of circulation, are not completely understood and might be relevant for individuals predisposed to hypertension. In this study we evaluate the interaction between adenosinergic and nitrergic systems in cell culture from the dorsomedial medulla oblongata of Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR). Using quantification of nitrite levels, RT-PCR analysis and RNA interference we demonstrate that adenosine A1 (A1R) and A2a receptor (A2aR) agonists induce a concentration-dependent decrease and increase of nitrite and nNOS mRNA levels in cultured cells from WKY and SHR, respectively. These effects in nitrite levels are attenuated by the administration of A1R and A2aR selective antagonists, CPT and ZM 241385. Furthermore, knockdown of A1R and A2aR show an increase and decrease of nNOS mRNA levels, respectively. Pretreatment with the nonselective inhibitor of NOS, L-NAME, abolishes nitrite-increased levels triggered by CGS 21680 in WKY and SHR cells. Finally, it is shown that the cAMP-PKA pathway is involved in A1R and A2aR-mediated decrease and increase in nitrite levels in SHR and WKY cells. Our results highlight the influence of adenosine on nitric oxide levels in cultured cells from dorsal medulla oblongata of neonate WKY and SHR rats. In part, the modulatory profile is different in the SHR strain.

Interaction of Orexin A and Vasopressin in the Brain Plays a Role in Blood Pressure Regulation in WKY and SHR Rats.

BackgroundOrexin A (OXA) and vasopressin (AVP) exert a central hypertensive effect due to an increase in sympathetic nerve activity. To date, little is known about the interaction of these 2 neuropeptides in the central regulation of blood pressure. The present study compared the consequences of infusion into the left cerebral ventricle (ICV) of OXA on mean arterial blood pressure (MABP) in normotensive (WKY) and spontaneously hypertensive (SHR) rats, and explored whether the central pressor action of OXA in these 2 strains depends on activation of brain AVP V1a receptors (V1aR).Material/MethodsTen groups of experiments were performed on 12-week-old WKY and SHR rats implanted with ICV cannulas for infusion of OXA (3 nmol) and V1aR antagonist (V1aRANT, 500 ng), administered separately and together. Levels of V1aR and OXR in the medulla oblongata of WKY and SHR rats were compared in separate series.ResultsWe found that: 1) OXA significantly increased MABP only in WKY rats, 2) V1aRANT prevented an increase in MABP induced by OXA in WKY rats and decreased MABP in SHR rats, 3) OXA abolished the hypotensive action of V1aRANT in SHR rats, and 4) SHR rats had significantly higher levels of OX1R and V1aR proteins and OX1R mRNA in the brain medulla.ConclusionsThe present study shows that OXA and AVP can interact in the brain to affect blood pressure regulation, and that this interaction differs in normotension and hypertension.

Involvement of NMDA receptors in tremor expression in Aspa/Hcn1 double-knockout rats.

We recently demonstrated that aspartoacylase (Aspa) and hyperpolarization-activated cyclic nucleotide-gated potassium channel 1 (Hcn1) genes were causative of essential tremor (ET) in rats. This finding was obtained using Aspaem34Kyo/Hcn1A354V double-mutant rats, but they were bred on a heterogeneous genetic background of two strains, F344 and WTC. Here, we developed an Aspaem34Kyo/Hcn1em1Kyo double-knockout rat strain with a homogenous F344 genetic background and studied the ability of glutamate receptor antagonists to suppress ET. The F344-Aspa/Hcn1 double-knockout rats exhibited spontaneous, intense body tremor equivalent to that in the double-mutant rats. N-acetyl-aspartate (NAA), a substrate of ASPA, showed accumulation in all brain regions and in the spinal cord. However, N-acetyl-aspartyl-glutamate (NAAG), which is derived from NAA and interacts with glutamatergic receptors, was decreased in the medulla oblongata of the double-knockout rats. The tremor was suppressed by 3-[(R)-2-carboxypiperazin-4-yl]-prop-2-enyl-1-phosphonic acid, an N-methyl-D-aspartate (NMDA) receptor antagonist, in F344-Aspa/Hcn1 double-knockout rats. The non-NMDA glutamate receptor antagonist NBQX weakly inhibited the tremor, while the metabotropic glutamate receptor antagonist LY341495 showed no effect. In addition, both NR2B subunit-specific (Ro 25-6981) and NR2C/NR2D subunit-specific (cis-piperidine dicarboxylic acid) NMDA receptor antagonists suppressed the tremor. These data indicated that the pathogenesis of tremor in Aspa/Hcn1 double-knockout rats involved ionotropic glutamate receptors, particularly NMDA receptors.

Insulin-responsive autonomic neurons in rat medulla oblongata.

Low blood glucose activates brainstem adrenergic and cholinergic neurons, driving adrenaline secretion from the adrenal medulla and glucagon release from the pancreas. Despite their roles in maintaining glucose homeostasis, the distributions of insulin-responsive adrenergic and cholinergic neurons in the medulla are unknown. We fasted rats overnight and gave them insulin (10 U/kg i.p.) or saline after 2 weeks of handling. Blood samples were collected before injection and before perfusion at 90 min. We immunoperoxidase-stained transverse sections of perfused medulla to show Fos plus either phenylethanolamine N-methyltransferase (PNMT) or choline acetyltransferase (ChAT). Insulin injection lowered blood glucose from 4.9 ± 0.3 mmol/L to 1.7 ± 0.2 mmol/L (mean ± SEM; n = 6); saline injection had no effect. In insulin-treated rats, many PNMT-immunoreactive C1 neurons had Fos-immunoreactive nuclei, with the proportion of activated neurons being highest in the caudal part of the C1 column. In the rostral ventrolateral medulla, 33.3% ± 1.4% (n = 8) of C1 neurons were Fos-positive. Insulin also induced Fos in 47.2% ± 2.0% (n = 5) of dorsal medullary C3 neurons and in some C2 neurons. In the dorsal motor nucleus of the vagus (DMV), insulin evoked Fos in many ChAT-positive neurons. Activated neurons were concentrated in the medial and middle regions of the DMV beneath and just rostral to the area postrema. In control rats, very few C1, C2, or C3 neurons and no DMV neurons were Fos-positive. The high numbers of PNMT-immunoreactive and ChAT-immunoreactive neurons that express Fos after insulin treatment reinforce the importance of these neurons in the central response to a decrease in glucose bioavailability.

Mitochondrial HSP60 Protein in Rat Medulla Oblongata Cells

HSP60 is a member of the heat shock protein (HSP) group and is located predominantly in cell mitochondria. Dysfunction and insufficient synthesis of HSP60 in the nervous system leads to neurodegeneration. The aim of the present work was to conduct immunohistochemical determination of the location of HSP60 protein in neurons and gliocytes in the medulla oblongata in rats. Studies were performed on mature male Wistar rats weighing 200–250 g (n = 7). The results provided evidence that HSP60 has a discrete localization in cytoplasmic structures in neurons and gliocytes. In large neurons, local accumulation of HSP60 allows fine structures to be detected, probably mitochondria. An important observation is that of the absence of any cytosolic reaction in medulla oblongata neurons and gliocytes. This provides grounds for using the reaction for HSP60 in complex studies of apoptosis in nerve cells, as this is associated with an accumulation of HSP60 and displacement of immunopositive product to the plasmalemma.

Synthesis, Characterization and Biocompatibility of N-palmitoyl L-alanine-based Organogels as Sustained Implants of Granisetron and Evaluation of their Antiemetic Effect

To assess the gelation power of N-palmitoyl L-alanine derivatives in injectable oils and to use the best chosen organogel as parenteral implant of granisetron for the treatment of emesis. Twelve N-palmitoyl L-alanine derived organogels were developed and evaluated in terms of morphology, thermal properties and in vivo performance. The ability of the selected formula to form in situ gel upon subcutaneous injection in rats and its biocompatibility were monitored over 2weeks by histopathological examination of the injection site. The acid derivative (N-palmitoyl L-alanine; PA) was superior to ester derivatives. The chosen formula (PA/safflower oil 10% w/v) was successful in forming an in situ gel of granisetron when subcutaneously injected in rats, lasting for 2weeks and proved to be biocompatible by histopathological examination. Moreover, it exerted an extended antiemetic activity by decreasing the cisplatin-induced pica for a duration of 96h and reduced preprotachykinin A mRNA expression and Substance P level for up to 4days (gastric tissue) or 5days (medulla oblongata) in rats. Granisetron organogel could be considered as a safe, sustained-release and supportive anticancer treatment in both acute and chronic emesis as well as an accompanying treatment with chemotherapeutics in cancer cases.

Hydrogen sulfide protects neonatal rat medulla oblongata against prenatal cigarette smoke exposure via anti-oxidative and anti-inflammatory effects

We previously demonstrated that hydrogen sulfide (H2S) protected neonatal rat medulla oblongata from prenatal cigarette smoke exposure (CSE) via anti-apoptotic effect. The present work further investigated the involvement of anti-oxidative and anti-inflammatory effects of H2S in the protection. Pregnant Sprague-Dawley rats were randomly divided into NaCl, CSE, CSE + NaHS (a donor of H2S) and NaHS groups. All the tests were performed with corresponding neonatal rats. Nissl staining revealed that NaHS treatment ameliorated neuronal chromatolysis in the hypoglossal nucleus and nucleus ambiguus resulted from prenatal CSE. Moreover, NaHS eliminated decrease of glutathione level, increase of malondialdehyde content and inhibition of superoxide dismutase activity within neonatal rat medulla oblongata caused by prenatal CSE. NaHS also relieved the up-regulation of tumor necrosis factor-α, interleukin-1β and interleukin-6 in the medulla oblongata of the neonatal CSE rats. These results suggest that H2S can alleviate prenatal CSE-induced injuries of neonatal rat medulla oblongata through anti-oxidative and anti-inflammatory effects.

NO-ergic Control of Blood Circulation in the Medulla Oblongata of Rats with Experimental Hemiparkinsonism under Prolonged Exposure to Continuous Light

The study was conducted on rats with unilateral damage to dopaminergic (DA) neurons in substantia nigra of the midbrain (experimental hemiparkinsonism). Degeneration of dopaminergic (DA) neurons was accompanied by hyperactivity of those neurons that remained intact and responded to apomorphine (Apo) test by rotational movements. Depending on the number of rotations, three groups of animals were defined. In the medulla oblongata of rats with unilateral damage to dopaminergic (DA) neurons, a significant increase in the activity of inducible NO-synthase (iNOS) was observed, while the activity of constitutive NO-synthase (cNOS) tended to decrease compared with that in control rats. An activation of neuronal NOsynthase (nNOS) in those rats by injections of L-arginine in the medullary nuclei was accompanied by weakening the hemodynamic effects compared to those in control rats. An exposure of animals to all-night light for three weeks was accompanied by increasing the number of damaged DA-ergic neurons in substantia nigra. At that, a significant decrease in cNOS activity in the medulla oblongata was observed, leading to the inhibition of de novo synthesis of nitric oxide (NO). The reduction of NO synthesis in the medulla oblongata neurons of rats with experimental hemiparkinsonism following their exposure to continuous light was also evidenced by the reduction of the amount of nitrite (NO2-) anion.

NO-ERGIC CONTROL OF BLOOD CIRCULATION IN THE MEDULLA OBLONGATA OF RATS WITH EXPERIMENTAL HEMIPARKINSONIZM UNDER EXPOSURE TO CONTINUOUS LIGHT.

The study was conducted on rats with unilateral damage to dopaminergic (DA) neurons in substantia nigra of the midbrain (experimental hemiparkinsonism). Degeneration of dopaminergic (DA) neurons was accompanied by hyperactivity of those neurons that remained intact and responded to apomorphine (Apo) test by rotational movements. Depending on the number of rotations, three groups of animals were defined. In the medulla oblongata of rats with unilateral damage to dopaminergic (DA) neurons, a significant increase in the activity of inducible NO-synthase (iNOS) was observed, while the activity of constitutive NO-synthase (cNOS) tended to decrease compared with that in control rats. An activation of neuronal NO-synthase (nNOS) in those rats by injections of L-arginine in the medullary nuclei was accompanied by weakening of the hemodynamic effects compared to those in control rats. An exposure of animals to continuous light for three weeks was accompanied by increasing the number of damaged DA-ergic neurons in substantia nigra. At that, a significant decrease in cNOS activity in the medulla oblongata was observed, leading to the inhibition of de novo synthesis of nitric oxide (NO). The reduction of NO synthesis in the medulla oblongata neurons of rats with experimental hemiparkinsonism following their exposure to continuous light was also evidenced by the reduction.

Hypoxia-induced increases in serotonin-immunoreactive nerve fibers in the medulla oblongata of the rat

Hypoxia induces respiratory responses in mammals and serotonergic neurons in the medulla oblongata participate in respiratory control. However, the morphological changes in serotonergic neurons induced by hypoxia have not yet been examined and respiratory controls of serotonergic neurons have not been clarified. We herein investigated the distribution of immunoreactivity for serotonin (5-hydroxytryptamine; 5-HT) in the medulla oblongata of control rats and rats exposed to 1–6h of hypoxia (10% O2). We also examined the medulla oblongata by multiple immunofluorescence labeling for 5-HT, neurokinin 1 receptors (NK1R), a marker for some respiratory neurons in the pre-Bötzinger complex (PBC), and dopamine β-hydroxylase (DBH), a marker for catecholaminergic neurons. The number of 5-HT-immunoreactive nerve cell bodies in the raphe nuclei was higher in rats exposed to hypoxia than in control rats. The number of 5-HT-immunoreactive nerve fibers significantly increased in the rostral ventrolateral medulla of rats exposed to 1–6h of hypoxia, caudal ventrolateral medulla of rats exposed to 2–6h of hypoxia, and lateral part of the nucleus of the solitary tract and dorsal motor nucleus of the vagus nerve of rats exposed to 1–2h of hypoxia. Multiple immunofluorescence labeling showed that 5-HT-immunoreactive nerve fibers were close to NK1R-immunoreactive neurons in ventrolateral medulla and to DBH-immunoreactive neurons in the medulla. These results suggest that serotonergic neurons partly regulate respiratory control under hypoxic conditions by modulating the activity of NK1R-expressing and catecholaminergic neurons.

Three-dimensional organization of the cytoplasmic neuroglobin-immunopositive structures in the rat medulla oblongata neurons

Neuroglobin is an iron-containing protein, most abundant in the vertebrate nervous system. Since neuroglobin is able to bind oxygen reversibly owing to the heme prosthetic group, it was believed that its function is an intercellular transport of oxygen in the nervous system and accumulation of oxygen for energy supply of cells in hypoxic conditions. In this work, a three-dimensional reconstruction of the neuroglobin distribution in large neurons of the rat medulla oblongata was carried out by means of immunocytochemistry and confocal laser microscopy. Positive neuroglobin immunocytochemical reaction was observed mainly in the perinuclear areas of large nerve cells exhibiting a discrete staining of the cytoplasm. Examination under the microscope at a high magnification revealed some neuroglobin-immunopositive granules, ring-like objects 1–2 μm in diameter, as well as linear and branched structures in neuronal cytoplasm and, occasionally, in the proximal segments of neuronal processes. Three-dimensional reconstruction of the neuroglobin-immunopositive structures showed that they mainly have the form of continuous lines and curves interlaced in some sites, about 1.0–1.5 μm thick, forming a complex network in the cytoplasm. The neuroglobin-immunopositive complexes found for the first time in neuronal cytoplasm are not identical to any known cytoplasmic compartments of nerve cells, but the diameter of their elements, as well as the shape and location suggest a possible link of neuroglobin with a mitochondrial network.

Effects of 5-HT3 receptor blockade on visceral nociceptive neurons in the ventrolateral reticular field of the rat medulla oblongata

The caudal ventrolateral medullary reticular formation is the first supraspinal level processing visce- ral nociceptive signals. In experiments on rats reactions of neurons of this zone to nociceptive stimulation of large intestine were examined and effects of selective blockade of 5-HT3-receptors on these reactions were assessed. According to the character or responses to nociceptive colorectal stimulation (CRS) the re- corded medullary cells were divided into three groups - excitated, inhibited and indifferent. Intravenous injection of 5-HT3-antagonist granisetron (1 and 2 mg/kg) as well as local application of the substance on medulla surface (1.25 and 2.5 nmole) suppressed dose-dependently background and evoked discharges of the reticular neurons excited by CRS but did not exert so much expressed influence on the cells inhibited by visceral nociceptive stimulation. Spike activity of the group of neurons indifferent to CRS under simi- lar conditions was of 5-HT3-independent character. The results obtained provide evidence that 5-HT3-re- ceptors mediate the facilitating effect of serotonin on the supraspinal transmission of abdominal nocicep- tive stimulus which, partly at least, is realized through selective activation of visceral nociceptive neurons of the medulla. The blocking of this mechanism may underlie the analgesic effect of 5-HT3-antagonists in a abdominal pain syndromes.

Immunolocalization of gaseous neurotransmitters in interneurons in the medulla oblongata in rats

We studied groups of internuclear interneurons (IN) that are located between the magnocellular and parvocellular reticular nuclei (IN1), reticular parvocellular nucleus, the nucleus of the solitary tract (IN2), and around the reticular lateral nucleus (IN3) that express the neuronal NO-synthase, cystathionine s-synthase, or heme oxygenase-2 in the medulla oblongata of Wistar rats using histochemical and immunohistochemical methods. We found local differences in the organization of INs. These differences were evident between IN1 cells, a cell group that consists of a relatively large number of large neurons, including giant cells, and IN2–IN3 cells. In interneurons of the latter two IN groups, we found significantly higher concentrations of cells and intensity of immunohistochemical staining. The local differences between the cells that contain cystathionine s-synthase were less pronounced than between other gaseous neurotransmitter interneurons. These data indicate that the internuclear interneurons have the structure that is necessary for the successful management of integration processes in the brain.