Early molecular events in the hippocampus of rats with streptozotocin-induced diabetes

In our study, we tried to find whether changes in expressions of inducible nitric oxide synthase (iNOS), corticosteroid (gluco-and mineralocorticoid) receptors (GRs and MRs, respectively), and bcl₂ protein within the early stages of streptozotocin (STZ)-induced diabetes in Wistar rats can be involved in hippocampal dysfunction. Expressions of iNOS and bcl₂ were studied using indirect immunofluorescence techniques, while GR and MR expressions were estimated using in situ mRNA hybridization. The concentrations of insulin, ACTH, and corticosterone in the blood serum were measured using ELISA kits. It was found that expression of iNOS in the CA2 and CA3 hippocampal areas increased significantly at day 3 after STZ injection, and corticosterone and ACTH levels in the serum increased at day 14. The iNOS expression was downregulated at day 14 of the development of diabetes. These changes were accompanied by significantly increased expression of GRs in the hippocampus. Neither bcl₂ nor MR expression increased in the CA2 and CA3 hippocampal areas within the examined period of the development of diabetes. Thus, we first obtained proof of noticeable early molecular events in the rat hippocampus related to experimental diabetes. These events may be linked with diabetes-associated cognitive decline observed in patients suffering from diabetes. Neirofiziologiya/Neurophysiology, Vol. 39, No. 6, pp. 498–502, November–December, 2007.     

Behavioral reactions of gerbils and structural alterations in their hippocampus after cerebral ischemia-reperfusion

We studied changes in behavior of Mongolian gerbils (Meriones unguiculatus) after ischemia-reperfusion of the brain (7-min-long occlusion of both arteriae carotis) and structural alterations in the hippocampus of such animals. Behavioral manifestations were observed under conditions of the open field test within 7 days of the postischemic period; immunofluorescent staining of brain sections with antibodies against specific proteins of neurons and glial cells was used. Motor hyperactivity reaching its maximum a day after ischemization and gradually decreasing within the postocclusion period was found in ischemized animals. On the 7th day, the level of locomotor activity in experimental gerbils was practically equal to that in the control group. In contrast, a postischemic decrease in the duration of episodes of resting was preserved for a longer time. A week after ischemia-reperfusion, intense delayed neuronal death and activation of glial cells were observed in the CA1 hippocampal area. Thus, cerebral ischemia-reperfusion results in significant transient disorders of behavioral phenomena in gerbils; at the same time, a clear correlation is observed between structural changes of neurons and the level of reactivity of glial cells in the hippocampus. These events can be significant aspects of the dynamics of postischemic damage to the above structure. Neirofiziologiya/Neurophysiology, Vol. 39, No. 6, pp. 458–467, November–December, 2007.     

Streptozotocin-Induced Diabetes Mellitus and Further Nimodipine Treatment Do Not Change Calcium Currents in Rat Sensory Neurons within Early Stages of the Disease

Earlier, considerable prolongation of the depolarization-induced Ca²⁺ transients was demonstrated in primary sensory neurons of rats with streptozotocin (STZ)-induced diabetes mellitus. To analyze the nature of this effect, we examine possible changes in the characteristics of voltage-operated calcium channels. Neither the amplitude of Ca²⁺ currents provided by both high- and low-voltage activated calcium channels nor the respective current densities significantly changed within the early stages of diabetes mellitus. In rats treated with nimodipine, also no significant changes in the calcium channel activity were observed. Only in the case of a decrease in the external calcium concentration was some drop in the Ca²⁺ current amplitude observed. We conclude that within the early stages of diabetes mellitus there are no significant modifications in the structure of the membrane of primary sensory neurons manifested in the expression of Ca²⁺ channels, which might be responsible for the observed rapidly occurring changes in calcium signalling, cytosolic Ca²⁺ accumulation, and synaptic plasticity.     

Influence of purinergic modulators on eEPSCs in rat CA3 hippocampal neurons: Contribution of ionotropic ATP receptors

ATP is considered to impact on fast synaptic transmission in several regions of the CNS, including the CA1 and CA3 areas of the hippocampus. The existing paradigm suggests that ATP induces synaptic responses in CA3 pyramidal cells, and a fast ATP-mediated component is observed in cultured hippocampal slices mainly under conditions of a synchronous discharge from multiple presynaptic inputs. We confirmed the existence of a fast ATP-mediated component within electrically evoked EPSCs (eEPSCs) in CA3 neurons of acute slices of the rat hippocampus using a whole-cell patch-clamp recording mode. In approximately 50% of the examined cells, eEPSCs were not completely inhibited by co-applied glutamate receptor antagonists, NBQX (50 μM) and D-APV (25 μM). The residual current was sensitive to ionotropic P2X receptor antagonists, such as suramin (25 μM) and NF023 (2 μM). Known purinergic receptor modulators, ivermectin (10 μM) and PPADS (10 μM), practically did not affect EPSCs, whereas a nonhydrolyzable ATP analog, ATPγS (100 μM), slightly decreased the EPSC amplitude. Moreover, ATPγS (100 μM) at a holding potential of −70 mV generated a slow inward current in most recorded neurons, which was insensitive to glutamate receptor antagonists. This fact is indicative of the ionotropic P2X receptor activation. Neirofiziologiya/Neurophysiology, Vol. 40, No. 1, pp. 21–29, January–February, 2008.     

Structural modifications of astrocytes in the hippocampus after experimental cerebral ischemia in gerbils

We studied reactions of astrocytes in the CA1 hippocampal zone of the mongolian gerbil (Meriones unguiculatus) after experimental short-lasting (7 min) cerebral ischemia resulting from bilateral occlusion of the carotid arteries. Immunocytochemical staining of hippocampal sections with antibodies against an astrocytes marker, glial fibrillary acidic protein (GFAP), was used. We measured the density of labelled cells in the layers of the CA1 zone at different time intervals (from 1 to 30 days) after cerebral ischemization. The number of labelled astrocytes within this period increased, and the dynamics of their density in different layers demonstrated significant dissimilarities. The earliest manifestations of reactive astrogliosis were observed in the hilus. The greatest rise in the number of astrocytes was found in the str. lacunosum-moleculare and str. moleculare on the 7th day, while in the str. pyramidale the maximum was reached only on the 14th day, which corresponded to the period of the highest intensity of delayed postischemic neuronal death. Thus, the intensity of morphological changes of the neurons and the level of reactivity of the astrocytes demonstrate a rather clear correlation; this fact can be one of the aspects of the dynamics of postischemic damage to the hippocampal neurons. Neirofiziologiya/Neurophysiology, Vol. 37, Nos. 5/6, pp. 410–415, September–December, 2005.     

State of the immediate-response gene <Emphasis Type="Italic">c-fos</Emphasis> in neurons of the hypothalamic suprachiasmatic nuclei of rats under conditions of modifications of the photocycle

The influence of modifications of normal photoperiodicity on the state of c-fos (gene of immediate functional response) in neurons of the suprachiasmatic nuclei (SChNs) of the rat hypothalamus was examined; samples were taken during the subjective day and night. In animals kept under normal conditions of alternation of light and darkness, expression of the product of this gene and marker of its activation (c-Fos protein) demonstrated a rather clear circadian pattern, with a greater level of the immunoreactivity of this protein at the day period. Constant illumination for 7 days disturbed the rhythm of the c-fos activity and smoothed circadian variations of the level of immunoreactivity of c-Fos. Under conditions of light deprivation of a similar duration, we observed a significant (more than twofold) increase in the indices of concentration of c-Fos and its content in the nuclei of SChN neurons, as well of the total content of this protein in SChN slices, at the day phase. Possible mechanisms of the influence of modifications of the photoperiod on the state of the c-fos gene in SChN cells, in particular the relation of the respective changes to variations of the level of melatonin, are discussed. It is emphasized that natural photoperiodicity and its experimental modifications result in noticeable shifts of the geometrical dimensions of the nuclei of SChN neurons. Neirofiziologiya/Neurophysiology, Vol. 40, No. 2, pp. 112–118, March–April, 2008.     

Neuronal MHC Class I Molecules are Involved in Excitatory Synaptic Transmission at the Hippocampal Mossy Fiber Synapses of Marmoset Monkeys

Several recent studies suggested a role for neuronal major histocompatibility complex class I (MHCI) molecules in certain forms of synaptic plasticity in the hippocampus of rodents. Here, we report for the first time on the expression pattern and functional properties of MHCI molecules in the hippocampus of a nonhuman primate, the common marmoset monkey (Callithrix jacchus). We detected a presynaptic, mossy fiber-specific localization of MHCI proteins within the marmoset hippocampus. MHCI molecules were present in the large, VGlut1-positive, mossy fiber terminals, which provide input to CA3 pyramidal neurons. Furthermore, whole-cell recordings of CA3 pyramidal neurons in acute hippocampal slices of the common marmoset demonstrated that application of antibodies which specifically block MHCI proteins caused a significant decrease in the frequency, and a transient increase in the amplitude, of spontaneous excitatory postsynaptic currents (sEPSCs) in CA3 pyramidal neurons. These findings add to previous studies on neuronal MHCI molecules by describing their expression and localization in the primate hippocampus and by implicating them in plasticity-related processes at the mossy fiber–CA3 synapses. In addition, our results suggest significant interspecies differences in the localization of neuronal MHCI molecules in the hippocampus of mice and marmosets, as well as in their potential function in these species.     

State of the NPY-ergic System of the Hypothalamic Arcuate Nucleus in Rats with Experimentally Induced Diabetes Mellitus

We have carried out a quantitative study of the state of a neuropeptide Y (NPY)-ergic system of the hypothalamic arcuate nucleus (AN) in rats in the norm and in streptozotocin (STZ)-induced diabetes mellitus. The NPY-containing objects were identified using an indirect immunofluorescent technique; a system of digital analysis of images and a special software were used. Analysis of the morphometric parameters of the NPY-immunopositive objects within the AN sections allowed us to classify in an automatic mode such objects as neurons of various sizes, fibers, and terminals, as well as to count the number of objects of each class. In addition, the fluorescent intensity of the objects under study (directly proportional to the concentration and amounts of NPY in these objects) was determined. On the basis of these parameters, criteria of the state of synthesis and secretion of NPY and NPY-ergic innervation in the AN subnuclei were proposed. In control animals, the greatest number of NPY-immunopositive neurons and total content of NPY in the neurons and terminals were observed in the ventrolateral and dorsomedial subnuclei of the AN (vl- and dmAN, respectively); this fact points to the high intensities of NPY synthesis and secretion in these structures. The greatest content of NPY in the nerve terminals within the vlAN zone is indicative of the highest intensity of NPY-ergic afferent influences on this subnucleus. It is concluded that the approach we proposed is adequate enough for integral quantitative estimation of the state of peptidergic systems. The development of STZ-induced diabetes mellitus caused changes in the NPY-ergic system in different AN subnuclei; such changes demonstrated certain specificity. In particular, an increase in the number of immunopositive neurons and the total content of NPY in the neurons of vlAN and the ventromedial AN subnucleus (vmAN), which is evidence in favor of intensification of synthesis of the neuropeptide, was not accompanied by an adequate rise in the NPY content in the terminals located in the subnucleus under study. The content of NPY in the eminentia medianus also decreased. The above data allow us to hypothesize that the NPY-ergic system of the AN under conditions of diabetes mellitus is functionally insufficient.     

Interaction of the monoaminergic and opioidergic brain systems in the course of nociceptive and antinociceptive reactions in cats

Nociceptive responses were evoked in cats by electrical transcutaneous stimulation of the forepaw or electrical stimulation of respective brain structures; these responses could be modulated (intensified or suppressed) by combined electrical stimulation of different brain structures or by neurochemical influences upon these structures. Intensification of nociceptive responses was observed after stimulation of the noradrenergic orP-ergic systems localized in the ventral zone of the central gray (vl SGC) and the structures monosynaptically connected with the latter: the posterior and lateral hypothalamic nuclei (Hp andHl) and preoptic region (RPO). Similar effects were induced by suppression of the serotoninergic system concentrated within the dorsolateral central gray (dl SGC), dorsal raphe nucleus (Rd), and closely related structures: the ventromedial, dorsomedial, and paraventricular hypothalamic nuclei (Hvm, Hdm, andHpv), septum (Sep), basolateral amygdalar nucleus (Am bl), fields 3–4 of the hippocampus (CA3–4), and cingular cortex (GC). Suppression of the serotoninergic system resulted in a decrease in the levels of functioning of the met-enkephalin- and β-endorphinergic systems and facilitation of theP-ergic system. Moderation of nociceptive responses, i.e., an analgesic effect, was observed after either stimulation of the serotonin-, met-enkephalin-, and β-endorphinergic systems localized in thedl SGC, Rd, Hvm, Hdm, Sep, Am bl, CA3–4, andGC, or suppression of the noradrenergic system. The latter influence resulted in inhibition of theP-ergic system and a rise in the functional activity of the met-enkephalin- and β-endorphinergic systems. The composition of two antagonistic brain systems, nociceptive and antinociceptive, is considered. The antinociceptive system includes serotonin-, met-enkephalin-, and β-endorphinergic elements. Leu-enkephalin is a nonspecific activator of the met-enkephalin-, β-endorphin-, andP-ergic systems. The nociceptive system consists of thevl SGC, Hp, Hl, andRPO, while the antinociceptive system includes thedl SGC, Rd, Hvm, Hdm, Hpv, Sep, Am dl, CA3–4, andGC.     

Computational experiments support a competitive function in the the CA3 region of the hippocampus

The comprehension of activities and functions of complex brain structures requires, among other things, information on simultaneous activities in several regions. Results reported in the literature using multi(micro/macro)electrode recordings or imaging techniques provide incomplete information due either to the small size and/or small number of investigated regions or to the poor spatiotemporal resolution, respectively. This is particularly true for the hippocampus and its subfields, and mathematical modeling and computer simulation have been used with the aim of obtaining information when this is lacking. Global activities in the CA3 field of the hippocampus, and in particular the genesis of theta rhythm and sharp waves, have been investigated here by a mathematical model formulated within the frame of a kinetic theory of neural systems. The model has taken into account data of experimental results both on different PSPs recorded in hippocampal neurons and on recurrent pyramidal collateral geometries. The computational ‘experiments’ to which the model was subjected suggest that the sharp waves arise through a selective and short block of the fast inhibitory neurons of CA3, produced by a medial septum inhibitory input, whereas the theta activity is produced by a durable, continuous inhibition of the slow inhibitory neurons. Information obtained also suggests that the recurrent pyramidal collaterals subserve a competitive, rather than a cooperative, organization. Based on these results a hypothesis on the possible functional organization of the CA3 field and of the entire hippocampus has been formulated. According to this hypothesis, the CA3 imposes a serial order on the flow of activity arriving at the hippocampus from the entorhinal cortex and from its connected polymodal cortical regions. This ordering permits cortical activities, arriving at CA3 on appropriate time intervals, to produce effects in regions of brain to which the CA3 projects. The competing cortical activities are lost.     

Effects of basolateral amygdalar nuclei on neuronal activity in the medullary respiratory center under hypoxia conditions

The effect of stimulation of the basolateral nuclei of the amygdala (ABL) on the impulse activity of respiratory neurons (RNs) of the rat medulla and the respiratory function was studied in the norm and under conditions of oxygen deficiency. Electrical stimulation of the ABL under conditions of normal atmospheric pressure exerted ambivalent effects on bulbar RNs; both activation and inhibition of these neurons were observed, but inhibitory effects noticeably prevailed. Electrical stimulation of the ABL within an initial phase of hypobaric hypoxia corresponding to ascent to a 4,000 to 5,000 m altitude exerted mostly inhibitory effects on the RN activity (similarly to what was observed under normoxia conditions). Stimulation of these nuclei within a phase of intensive hypoxia (7,500 to 8,000 m) evoked no typical responses of such neurons against the background of hypoxic suppression of their activities. Neirofiziologiya/Neurophysiology, Vol. 38, No. 4, pp. 292–297, July–August, 2006.     

Coupling of c-fos expression in the spinal cord and amygdala induced by dorsal neck muscles fatigue

c-fos gene expression in the cervical spinal cord and amygdala was examined in anaesthetized rats following muscle fatigue caused by intermittent high-rate (100 s⁻¹) electrical stimulation of the dorsal neck muscles (m. trapezius and m. splenius). Fatigue-related increases in c-fos expression were observed on the stimulated muscle side in the cervical C2–C4 (layers 1, 3–5, 7 and 10) spinal segments, bilaterally in the lumbar L4–L6 (layer 1) segments and in contralateral central (Ce), medial (Me), and basomedial (BM) amygdaloid nuclei. A scarce number of staining cells were found within lateral and basolateral nuclei. The rostro-caudal extent of c-fos expression in the spinal cord supports functional coupling of the cervical and lumbar regions during the neck muscle fatigue development. The distinct c-fos expression in the Ce and Me amygdaloid nuclei suggests that they may contribute to mediating the neck muscle fatigue-related nociception, autonomic and behavioural responses.     

Corticofugal effects on the neuronal activity in the emotiogenic/motivational zones of the hypothalamus

Neuronal responses to stimulation of the proreal (field 8) and cingular (field 24) cortices, pyriform lobe (periamygdalar cortex), and hippocampus (CA3) were studied in the lateral (HL) and ventromedial (Hvm) hypothalamus, dorsal hypothalamic region (aHd), and projection region of the medial forelimb bundle (MFB); single and repeated (series of a 6–300 sec⁻¹ frequency) stimuli were used. At single stimulations, the minimum proportion of inhibitory responses with respect to excitatory effects was observed when the neocortex (the proreal gyrus) was stimulated; this proportion became successively greater at stimulations of the intermediate cortex (the cingular gyrus) and paleocortex (the pyriform cortex), while stimulation of the archicortex (the hippocampus) evoked mostly inhibitory responses. At repeated stimulation of the cortical structures, inhibitory responses prevailed in the neurons under study: their total number was nearly four times larger than that of excitatory reactions. The response patterns to single and serial stimulations of the cortical structures allowed us to demonstrate: (i) significant diversity of the influences received by hypothalamic neurons from the cortical structures and (ii) the dependence of the pattern of these influences on the phylogenetic specificity of the above structures.     

Changes in the Functioning of Ca2+-ATPases of Rat Exocrine Cells in Experimental Diabetes Mellitus

It is obvious that disruption of functions of the nervous system in diabetes mellitus is to a great extent related to the changes of synthesis or exocytosis of neurotransmitters. Since the mechanisms underlying exocytosis are similar in cells of different types, it may be assumed that studying these mechanisms in secretory cells will allow experimenters to obtain information on ways to control this process in neurons. Based on the supposition that changes in the activity of Ca2+-controlling systems in exocrine cells play an important role in functional disorders in the salivary glands in diabetes mellitus, we demonstrated, using the fura-2/AM dye, that the intracellular calcium concentration ([Ca²⁺] _i ) in secretory cells of the above glands in rats with streptozotocin-induced diabetes mellitus (being in the resting state) is significantly increased (on average, by 65%). In our study, we showed that Ca²⁺-ATPases play an important role in the control of calcium homeostasis in secretory cells of salivary glands in diabetes mellitus. In particular, we demonstrated that the kinetic parameters of microsomal Ca²⁺-ATPases decreased: V ₀, by 50 ± 7, and P _max, by 52 ± 6%, on average. In diabetes mellitus, V _max of Ca²⁺-ATPases also dropped significantly, by 47 ± 8 and 79 ± 9%, on average, for PMCA and SERCA, respectively. The decrease in K _ATP was 71 ± 11% for SERCA and that in K _Ca was 92 ± 3% for PMCA. We concluded that the activity of Ca²⁺-ATPases of secretory cells in diabetes mellitus is suppressed because of a decrease in the turnover and/or in the specific number of active molecules of the enzyme.     

Immunohistochemical localization of the angiotensin-(1–7) receptor Mas in the murine forebrain

Apart from the well-known biologically active angiotensin II, other biologically active angiotensins have been discovered, including angiotensin IV and angiotensin-(1–7). Some years ago, we and others discovered that the Mas proto-oncogene encodes a receptor that is essential for angiotensin-(1–7) signaling. Angiotensin-(1–7) is not only expressed in the periphery but also within the brain. Based on that, we examined the distribution of Mas within the murine brain, using an antibody directed against the 3^rd cytoplasmic loop of the receptor protein. Strongest Mas protein expression was detected in the dentate gyrus of the hippocampus and within the piriform cortex. However, Mas protein expression is not restricted to these areas, since Mas immunopositive neurons were also seen in different parts of the cortex, hippocampus, amygdala, basal ganglia, thalamus and hypothalamus. Based on the expression of Mas protein in the cortex and the limbic system, angiotensin-(1–7) signaling may play a role in synaptic plasticity, learning, memory and emotion, as has been described for angiotensin II and IV.     

AMPA-Induced Excitotoxicity Increases Nuclear Levels of CAD, Endonuclease G, and Acinus and Induces Chromatin Condensation in Rat Hippocampal Pyramidal Neurons

Programmed cell death has been linked to AMPA-receptor-mediated excitotoxicity in pyramidal neurons of the hippocampus. The intent of this study was to investigate the roles of caspase-dependent and independent nuclear death-related factors in mediating AMPA-induced nuclear changes in PyNs by use of immunohistochemistry and transmission electron microscopy (TEM). Data indicate increases in the nuclear levels of caspase-activated acinus and DNase and Endonuclease G (a caspase-independent endonuclease) in CA1 and CA3 PyN nuclei with different temporal patterns following an AMPA-insult. Hoechst staining and TEM confirm AMPA-induced chromatin condensation. The presence of active acinus in nuclei suggests it mediates chromatin condensation. Interestingly, a DNA fragmentation labeling protocol showed that there was no chromatin cleavage up to 90 min after AMPA-insult. Overall, we conclude that: 1) AMPA-induced excitotoxicity increases nuclear immunoreactivity of pro-death enzymes from multiple programmed cell death pathways, 2) differential chromatin condensation patterns occur between CA1 and CA3, and 3) there is no chromatin cleavage within our experimental timeframe. Abbreviations: AIF, apoptosis inducing factor; AMPA, α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid; CAD, caspase-activated DNase; CIP, calf intestinal alkaline phosphatase; EndoG, endonuclease G; ICAD, inhibitor of CAD; NMDA, N-methyl D-aspartate; TdT, terminal deoxynucleotidyl transferase; TEM, transmission electron microscopy; TUNEL, terminal deoxynucleotidyl transferase biotin-UTP nick end labeling     

Prenatal stress causes dendritic atrophy of pyramidal neurons in hippocampal CA3 region by glutamate in offspring rats

A substantial number of human epidemiological data, as well as experimental studies, suggest that adverse maternal stress during gestation is involved in abnormal behavior, mental, and cognition disorder in offspring. To explore the effect of prenatal stress (PS) on hippocampal neurons, in this study, we observed the dendritic field of pyramidal neurons in hippocampal CA3, examined the concentration of glutamate (Glu), and detected the expression of synaptotagmin‐1 (Syt‐1) and N‐methyl‐D ‐aspartate receptor 1 (NR1) in hippocampus of juvenile female offspring rats. Pregnant rats were divided into two groups: control group (CON) and PS group. Female offspring rats used were 30‐day old. The total length of the apical dendrites of pyramidal neurons in hippocampal CA3 of offspring was significantly shorter in PS than that in CON (p < 0.01). The number of branch points of the apical dendrites of pyramidal neurons in hippocampal CA3 of offspring was significantly less in PS (p < 0.01). PS offspring had a higher concentration of hippocampal Glu compared with CON (p < 0.05). PS offspring displayed increased expression of Syt‐1 and decreased NR1 in hippocampus compared with CON (p < 0.001 and p < 0.01, respectively). The expression of NR1 in different hippocampus subfields of offspring was significantly decreased in PS than that in CON (p < 0.05‐0.01). This study shows that PS increases the Glu in hippocampus and causes apical dendritic atrophy of pyramidal neurons of hippocampal CA3 in offspring rats. The decline of NR1 in hippocampus may be an adaptive response to the increased Glu. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2010     

NADPH-Diaphorase-containing neurons in the medullary structures involved in generation of the respiratory activity in neonatal rats

Using a histochemical technique, we examined distribution of the neurons containing a marker of nitric oxide synthase (NOS), NADPH-diaphorase (NADPH-d), on frontal slices of the medulla and upper cervical spinal segments of 4-day-old rats. It was demonstrated that NADPH-d-positive cells are present within the dorsal and ventral medullary respiratory groups. The highest density of the labeled middle-size multipolar neurons (27.9±2.6 cells per 0.1 mm² of the slice) was observed in the rostral part of the ventral respiratory group, within the reticular lateral paragigantocellular nucleus. Similar NADPH-d-positive neurons were also observed in other reticular formation structures: rostroventrolateral reticular, gigantocellular, and ventral medullary nuclei, and in the ventral part of the paramedial nucleus. There were no labeled neurons in the lateral reticular nucleus. Single small and medium-size labeled neurons were found at all rostro-caudal levels of thenucl. ambiguous (nuclei retrofacialis, ambiguous, andretroam-biguous). Groups of NADPH-d-positive neurons were also revealed within the dorsal respiratory group, along the whole length of thenucl. tractus solitarii (mostly in its ventrolateral parts). Single labeled neurons were also observed in thenucl. n. hypoglossi, and their groups were observed in the dorsal motor part of thenucl. n. vagus. Involvement of the structures containing NADPH-d-positive neurons in the processes related to generation of the respiratory activity is discussed. Our neuroanatomical experiments prove that in early postnatal mammals NO is actively involved in generation and regulation of the medullary respiratory rhythm. Neirofiziologiya/Neurophysiology, Vol. 32, No. 2, pp. 128–136, March–April, 2000.     

Expression and Changes of Hyperoxidized Peroxiredoxins in Non-Pyramidal and Polymorphic Cells in the Gerbil Hippocampus During Normal Aging

Oxidative stress is one of predisposing factors to age-related neurodegeneration in the brain. In particular, thiol-containing groups are susceptible to oxidative stress, which induces the formation of the disulfide bond and/or hyperoxidized form of thiol-containing proteins. We observed the protein thiol levels in the hippocampal homogenates and also investigated changes in hyperoxidized form of peroxiredoxin (Prx–SO₃) immunoreactivity and proteins levels in the gerbil hippocampal subregions during normal aging. Levels of total thiol, non-protein thiol, and protein thiol were decreased in the hippocampal homogenates with age. At post-natal month 1 (PM 1), pyramidal and non-pyramidal cells in the hippocampal CA1 region (CA1) showed Prx–SO₃ immunoreactivity. Prx–SO₃ immunoreactivity in the cells was decreased by PM 12, thereafter, Prx–SO₃ immunoreactivity in the cells increased again with age. In the CA2/3, Prx–SO₃ immunoreactivity in pyramidal cells was not significantly changed; however, the immunoreactivity in pyramidal cells was very low at PM 12. Prx–SO₃ immunoreactivity in the dentate gyrus (DG) was distinctly changed during aging. At PM 1, Prx–SO₃ immunoreactivity in granule and polymorphic cells was weak and strong, respectively. The immunoreactivity in the neurons was decreased with age, not shown in any neurons at PM 12. Thereafter, Prx–SO₃ immunoreactivity increased again with age. In addition, Prx–SO₃ protein level in the hippocampus was lowest at PM 12. These results suggest that thiol-containing proteins are changed during aging and Prx–SO₃ immunoreactivity was different according to cells in the hippocampal subregion during aging.