Glutamatergic pathways from the Kölliker-Fuse nucleus to the phrenic nucleus in the rat

After ipsilateral injections of biotinylated dextran amine (BDA) into the K?lliker-Fuse (KF) nucleus and cholera toxin B subunit (CTb) into the ventral horn in C4 to C5 segments of the spinal cord, an overlapping distribution of BDA-labeled axon terminals and CTb-labeled neurons was found in the rostral ventral respiratory group (rVRG) region ipsilateral to the injection sites. After ipsilateral injections of BDA into the KF and Fluoro-Gold (FG) into the ventral horn in C4 to C5 segments of the spinal cord, BDA-labeled axons were found to make asymmetrical synapses with the somata and dendrites of FG-labeled neurons within the neuropil of the rVRG region. Using retrograde tracing combined with immunohistochemistry for phosphate-activated glutaminase (PAG), we observed that as many as 72% of the rVRG neurons projecting to the PhN were immunoreactive for PAG and that approximately 62% and 75% of the KF neurons projecting respectively to the rVRG region and PhN contain PAG immunoreactivity. Using anterograde tracing combined with immunohistochemistry for vesicular glutamate transporter 2 (VGluT2), we further demonstrated that the KF axon terminals in the rVRG and PhN regions as well as the rVRG axon terminals in the PhN region contain VGluT2 immunoreactivity. The present results suggest that the glutamatergic pathways from the KF to the PhN directly and indirectly via the rVRG region may exist and underlie the inspiratory responses that are elicited by activation of the KF neurons.     

Estrogen attenuates antinociception produced by stimulation of Kölliker-Fuse nucleus in the rat

This is the first demonstration of sex‐related differences in the α₂‐adrenoceptor‐mediated antinociceptive effects produced by stimulation of an endogenous noradrenergic pathway. Electrical or chemical (substance P) stimulation of Kölliker–Fuse nucleus (KF, A7) is known to produce antinociception mediated by α₂‐adrenoceptors in the spinal cord. KF stimulation has also been shown to inhibit the responses of nociceptive neurons in the dorsal horn of the medulla and the spinal cord. We investigated whether KF stimulation produces sex‐specific modulation of trigeminal nociception. The N‐methyl‐d ‐aspartic acid (NMDA)‐induced nociceptive behavior was employed as an index of nociception. Microinjection of NMDA (2 nmol/10 µL) in the trigeminal region produced nociceptive scratching behavior that was confined to the orofacial region. Male and ovariectomized (OVX) Sprague–Dawley rats were implanted with a guide cannula dorsal to the KF nucleus and a PE‐10 cannula in the trigeminal region dorsal to obex. Nociceptive testing was conducted after 5–7 days of recovery. A group of ovariectomized rats (OVX+E) was treated with estradiol benzoate 48 h prior to nociceptive testing. There were no significant differences in the number of NMDA‐induced scratches or duration between the male, OVX and OVX+E groups. Microinjection of substance P (3.7 pmol/0.5 µL) in the KF significantly reduced the number of NMDA‐induced scratches and their duration in male and OVX groups; these were restored to control levels by yohimbine (30 µg/15 µL), an α₂‐adrenoceptor antagonist. However, KF stimulation failed to inhibit the NMDA‐induced scratching behavior in the OVX+E group. We conclude that stimulation of KF produces estrogen‐dependent modulation of nociception.     

Phrenic motoneurons receive monosynaptic inputs from the Kölliker-Fuse nucleus: a light- and electron-microscopic study in the rat

The parabrachial complex, which plays an important role in respiratory regulation, has been reported to send projection fibers to the phrenic nucleus, but the synaptic organization between the parabrachial fibers and the phrenic motoneurons has not been examined. Using anterograde and retrograde tracing methods, we found in the rat that the parabrachial fibers originating mainly from the K?lliker-Fuse nucleus (KF) terminated not only within the phrenic nucleus but also on the radial dendritic bundles of the phrenic motoneurons. It was further revealed that the KF fibers made asymmetrical synapses predominantly with dendrites and partly with somata of the phrenic motoneurons. These data suggest that output signals from the KF may exert excitatory influence directly upon the phrenic motoneurons.     

The Kölliker-Fuse nucleus gates the postinspiratory phase of the respiratory cycle to control inspiratory off-switch and upper airway resistance in rat

Lesion or pharmacological manipulation of the dorsolateral pons can transform the breathing pattern to apneusis (pathological prolonged inspiration). Apneusis reflects a disturbed inspiratory off‐switch mechanism (IOS) leading to a delayed phase transition from inspiration to expiration. Under intact conditions the IOS is irreversibly mediated via activation of postinspiratory (PI) neurons within the respiratory network. In parallel, populations of laryngeal premotoneurons manifest the IOS by a brief glottal constriction during the PI phase. We investigated effects of pontine excitation (glutamate injection) or temporary lesion after injection of a GABA‐receptor agonist (isoguvacine) on the strength of PI‐pool activity determined from respiratory motor outputs or kinesiological measurements of laryngeal resistance in a perfused brainstem preparation. Glutamate microinjections into distinct parts of the pontine Kölliker‐Fuse nucleus (KF) evoked a tonic excitation of PI‐motor activity or sustained laryngeal constriction accompanied by prolongation of the expiratory phase. Subsequent isoguvacine microinjections at the same loci abolished PI‐motor or laryngeal constrictor activity, triggered apneusis and established a variable and decreased breathing frequency. In summary, we revealed that excitation or inhibition of defined areas within the KF activated and blocked PI activity and, consequently, IOS. Therefore, we conclude, first, that descending KF inputs are essential to gate PI activity required for a proper pattern formation and phase control within the respiratory network, at least during absence of pulmonary stretch receptor activity and, secondly, that the KF contains large numbers of laryngeal PI premotor neurons that might have a key role in the regulation of upper airway resistance during reflex control and vocalization.     

Cytoarchitectural organization of the parabrachial/Kölliker-Fuse complex in man

While the parabrachial/K?lliker-Fuse complex has been described in a variety of animal species it has not been characterized in human brainstem. In the present study we investigated fetal and infant brainstems, focusing particularly on the dorsolateral part of the pontine tegmentum, with the aim of defining the precise cytoarchitecture of the medial parabrachial, lateral parabrachial, and K?lliker-Fuse nuclei in man, and analyzing the developmental stages of this complex. In serial sections of 28 human brainstems of subjects aged between 32 gestational weeks and 1 year we made a morphologic and morphometric analysis of the shape and size of the parabrachial/K?lliker-Fuse complex. We observed a homogeneous morphology in all cases, which enabled us to define the structure of the three nuclei. The features of the parabrachial nuclei are largely consistent with those reported in experimental studies. However, the K?lliker-Fuse nucleus appears to be more developed in human beings than in other animal species, showing a greater extension and a more complex structure. The neuronal maturation of these nuclei was seen to occur between the 35th and the 36th gestational weeks.     

Developmental changes of serotonin 4(a) receptor expression in the rat pre-Bötzinger complex

Serotonin receptors (5-HTRs) are known to be involved in the regulation of breathing behavior and to mediate neurotrophic actions that exert a significant function in network formation during development. We studied neuronal 5-HT(4(a))R-immunoreactivity (-IR) at developmental ages from E14 to P10. Within the pre-B?tzinger complex (pre-B?tC), a part of the respiratory network important for rhythmogenesis, 5-HT(4(a))R-IR was most extensive in rats at an age of E18. The 5-HT(4(a))-IR was found predominantly in the neuropil, whereas somatic staining was sporadic at late embryonic (E18-E20) stages. At birth, we observed a dramatic change to a predominantly somatic staining, and neuropil staining was greatly reduced and disappeared at an age of P4. In all developmental stages, 5-HT(4(a)) and mu-opioid receptors were strongly coexpressed in neurons of the pre-B?tC, whereas 5-HT(4(a))R expression was absent in neurons within the dorsal horn. Nestin, a marker for CNS progenitor cells, was used to obtain information about the degree of pre-B?tC differentiation. Nestin-positive cells did not appear within the pre-B?tC before age E20. At E16, nestin-expressing cells were absent in the nucleus ambiguus (NA) and its ventral periphery. The number of nestin-positive cells increased after birth within and outside the pre-B?tC, the majority of cells being glial. Coexpression of nestin and 5-HT(4(a))R was localized predominantly within the NA and appeared only sporadically within the pre-B?tC. We conclude that 5-HT(4(a))Rs are important not only for neuromodulation of cellular excitability but also for respiratory network formation.     

Role of β3-adrenergic receptor in the modulation of synaptic transmission and plasticity in mouse cerebellar cortex

Convergent lines of evidence have recently highlighted β3-adrenoreceptors (ARs) as a potentially critical target in the regulation of nervous and behavioral functions, including memory consolidation, anxiety, and depression. Nevertheless, the role of β3-ARs in the cerebellum has been never investigated. To address this issue, we first examined the effects of pharmacological manipulation of β3-ARs on motor learning in mice. We found that blockade of β3-ARs by SR 59230A impaired the acquisition of the rotarod task with no effect on general locomotion. Since the parallel fiber–Purkinje cell (PF–PC) synapse is considered to be the main cerebellar locus of motor learning, we assessed β3-AR modulatory action on this synapse as well as its expression in cerebellar slices. We demonstrate, for the first time, a strong expression of β3-ARs on Purkinje cell soma and dendrites. In addition, whole-cell patch-clamp recordings revealed that bath application of β3-AR agonist CL316,243 depressed the PF–PC excitatory postsynaptic currents via a postsynaptic mechanism mediated by the PI3K signaling pathway. Application of CL316,243 also interfered with the expression of PF long-term potentiation, whereas SR 59230A prevented the induction of LTD at PF–PC synapse. These results underline the critical role of β3-AR on cerebellar synaptic transmission and plasticity and provide a new mechanism for adrenergic modulation of motor learning.     

Tumor necrosis factor-α impairs the recovery of synaptic transmission from hypoxia in rat hippocampal slices

Cerebral ischaemia is a common occurrence in a range of pathological conditions, including stroke and traumatic brain injury. Two of the components in ischaemia are tissue hypoxia and the release of pro-inflammatory agents such as TNF-α. The role of TNF-α in an ischaemic/hypoxic episode is still controversial, although deleterious effects of pro-inflammatory cytokines in the area of injury are well documented. One of the prime adaptive mechanisms in response to hypoxia is the cellular activation of adenosine 1 receptors (A1Rs), which inhibits excitatory synaptic transmission. In the present study we have examined the effect of TNF-α application on synaptic transmission during hypoxic exposure and re-oxygenation using extracellular recordings in the CA1 region of the rat hippocampal slice. Hypoxia caused a reversible depression of the field EPSP (29.6 ± 9.7% of control, n = 5), which was adenosine A₁ receptor-dependent (85.7 ± 4.3%, in the presence of DPCPX (200 nM), the adenosine A₁ receptor antagonist). DPCPX inhibited the maintenance of long-term potentiation obtained 30 min post hypoxia (143.8 ± 8.2% versus 96.4 ± 10.6% respectively, 1 h post tetanus; n = 5; p < 0.005). In TNF-α (150 pM) treated slices hypoxic depression was similar to controls but a reduction in fEPSP slope was observed during re-oxygenation (66.8 ± 1.4%, n = 5). This effect was reversed by pre-treatment with SB 203580 (1 µM), a p38 MAP kinase inhibitor (91.8 ± 6.9%, n = 5). These results demonstrate a novel p38 MAPK dependent role for TNF-α in attenuating synaptic transmission after a hypoxic episode.     

Do Ca2+ channels share NMDA receptors in plasticity of synaptic transmission in the rat visual cortex?

We examined the involvement of Ca2+ channels in LTP of responses in rat visual cortex slices. Stimulating layer IV, field potentials including EPSP1 and EPSP2 from layer II/III were recorded. L-type Ca2+ channel blocker nifedipine did not have a considerable effect on LTP of the responses. T-type Ca2+ channel blocker Ni2+ decreased potentiation of EPSP1 and almost blocked that of EPSP2. Effect of visual experience on the function of the channels is also considered. These results indicate that T-type Ca2+ channels play a real role in stable LTP of EPSP2. Also the function of the channels was almost the same in dark and light reared visual cortices.     

In vivo synaptic transmission in the zebra finch high vocal center and robust nucleus of the arcopallium after different stimulus patterns**★

BACKGROUND： Electrophysiological studies using brain slices have revealed that the developmental regulation of synaptic plasticity in vocal learning pathway is essential for song learning in zebra finches. Publications reporting in vivo electrophysiological investigation are scarce. Many aspects of neural mechanisms underlying song learning and production still remain uncertain. OBJECTIVE： To observe the efficacy of paired pulses and the effect on synaptic transmission induced by low-frequency stimulations, high-frequency stimulations, and theta-burst stimulations. DESIGN, TIME AND SETTING： A comparative observation. The experiment was conducted from October 2006 to October 2007 in the Neurophysiology Laboratory of South-China Normal University. MATERIALS： Twenty-four adult male zebra finches were supplied by the Department of Animal Experiment of College of Life Sciences, South China Normal University. A SEN-7203 stimulator （NIHON KOHDEN）, as well as a DSJ-731WF microelectrode amplifier and DSJ-F amplifier （provided by South-China Normal University）, were used to stimulate and record, respectively. METHODS： Animals were randomly divided into low-frequency, high-frequency, and theta-burst frequency stimulation groups. After recording evoked potentials, an input-output curve was evaluated. Subsequently, the efficacy of paired pulses with different stimulus intensity （1/3, 1/2, 2/3, or 3/4 of the value that induced the largest synaptic response）, as well as interpulse intervals （50, 75, and 100 ms）, was measured in each group. The test stimulus intensity was set to a level that evoked 1/2 or 1/3 amplitude of the maximum response. MAIN OUTCOME MEASURES： Changes in amplitude, slope, and area of evoked potentials elicited by different stimulus patterns. RESULTS： （1） Efficacy of paired pulses： there was significant paired-pulse facilitation in the high vocal center and robust nucleus of the arcopallium （HVC-RA） synapse. Efficacy decreased when paired-pulse intervals or stimulus i     

Co-expression of calretinin and parvalbumin in the rat facial nucleus**★

BACKGROUND： Calretinin and parvalbumin are members of the intracellular calcium binding protein family, which transform Ca^2＋ bioinformation into regulation of neuronal and neural network activities. OBJECTIVE： To observe expression and co-expression of calretinin and parvalbumin in rat facial nucleus neurons . DESIGN, TIME AND SETTING： Neuronal morphology experiment was performed at the Research Laboratory of Applied Anatomy, Department Neurobiology and Anatomy, Xiangya Medical College of Central South University from August to October 2007. MATERIALS： Five healthy, adult Sprague Dawley rats were selected. Polyclonal rabbit-anti-parvalbumin and mouse-anti-calretinin were provided by Sigma, USA. METHODS： Rat brains were obtained and cut into coronal slices using a freezing microtome. Slices from the experimental group were immunofluorescent stained with polyclonal rabbit-anti-parvalbumin and mouse-anti-calretinin antibodies. The control group sections were stained with normal rabbit and mouse sera. MAIN OUTCOME MEASURES： Immunofluorescent double-staining was used to detect calretinin and parvalbumin expression. Nissl staining was utilized for facial nucleus localization and neuronal morphology analysis. RESULTS： The majority of facial motor neurons was polygon-shaped, and expressed calretinin and parvalbumin. The calretinin-immunopositive neurons also exhibited parvalbumin immunoreactivity, that is, calretinin and parvalbumin were co-expressed in the same neuron. CONCLUSION： Calretinin and parvalbumin were expressed in facial nucleus neurons, with varied distribution.     

Quantitative changes in number of “synaptic” ribbons in rat pinealocytes after orchidectomy and in organ culture

Summary A quantitative study of synaptic ribbons in rat pinealocytes was performed after orchidectomy and in organ culture. Both orchidectomy and culturing the pineal organ caused an increase in number and size of these structures.Present study indicate that microtubular sheaves and/or microtubules may represent precursors of synaptic ribbons.It is suggested that synaptic ribbons of rat pinealocytes, far from being phylogenetic relics of no functional significance play a role in the function of the pineal organ. An exact functional interpretation of the synaptic ribbons, however, is still a matter of conjecture.In gratitude and with admiration this paper is dedicated to Professor Dr. J. Ariëns Kappers.     

Priming stimulation modifies synaptic plasticity in the perforant path of hippocampal slice in rat

1 Introduction The ability to modify synaptic strength in an activity- dependent manner, either as long-term depression (LTD) or as long-term potentiation (LTP) is a fundamental feature of most central nervous system synapses. The properties of different forms of LTP in the rodent hippocampus have been exceedingly well studied. A less well studied but par- ticularly intriguing finding is that the capacity of many syn- apses for plastic changes itself is subject to modulation of subsequent …     

Pre- and postsynaptic effects of norepinephrine on γ-aminobutyric acid-mediated synaptic transmission in layer 2/3 of the rat auditory cortex

Noradrenergic terminals from the locus coeruleus release norepinephrine (NE) throughout most brain areas, including the auditory cortex, where they affect neural processing by modulating numerous cellular properties including the inhibitory γ-aminobutyric acid (GABA)ergic transmission. We recently demonstrated that NE affects GABAergic signaling onto cortical pyramidal cells in a complex manner. In this study, we used a combination of patch-clamp recording and immunohistochemical techniques to identify the synaptic site and the location of the adrenergic receptors involved in the modulation of GABAergic signaling in cortical layer 2/3 of the rat. Our results showed that NE increases the frequency of spike-independent miniature inhibitory postsynaptic currents (mIPSCs), as well as the probability of release of unitary inhibitory postsynaptic currents (IPSCs) obtained with patch-clamp pair-recordings. The pharmacology of mIPSCs and the identification of adrenergic receptors in neurons containing the GABAergic marker parvalbumin (PV) suggest that NE increases the presynaptic probability of GABA release by activating α(2) - and β-receptors on PV-positive neurons. On the contrary, bath-applied NE or phenylephrine, decreased the current mediated by pressure application of the GABA(A) -receptor agonist muscimol, as well as the amplitude-but not the frequency-of mIPSCs, indicating that activation of postsynaptic α(1) adrenoceptors reversibly depressed GABAergic currents. We speculate that while a generalized postsynaptic decrease of GABAergic inhibition might decrease the synaptic activation threshold for pyramidal neurons corresponding to an alert state, NE might promote perception and sensory binding by facilitating lateral inhibition as well as the production of γ-oscillations by a selective enhancement of perisomatic inhibition.     

Effect of electroacupuncture on synaptic transmission in dentate gyrus of the hippocampus in cerebral ischemic injured rats

IN T R O D U C T IO N Long-term potentiation (LTP ) is an essentialphenom enon concern- ing cerebral plasticity. It w as routinely used as a basic cellular m odel for the study of m em ory. LTP could be induced by m ul- ti-factors constructing the externa…     

Evolution of Alzheimer’s disease-related cytoskeletal changes in the basal nucleus of Meynert

This study examines the evolution of Alzheimer's disease (AD)-related pathology in a subcortical predilection site, the basal nucleus of Meynert (bnM), which is a major source of cortical cholinergic innervation. Brains of 51 autopsy cases were studied using silver techniques and immunostaining for tau-associated neurofibrillary pathology and for amyloid beta protein (Abeta) deposits. All cases are classified according to a procedure permitting differentiation of six stages of AD-related neurofibrillary changes in the cerebral cortex. Initial cytoskeletal abnormalities in the bnM are already noted in stage I of cortical neurofibrillary changes. The gradual development of the neurofibrillary pathology in the bnM parallels the progression of the AD-related stages in the cerebral cortex. A variety of morphologically distinguishable cytoskeletal alterations are observed in large nerve cells which predominate in the bnM. Based on these cellular alterations, a sequence of cytoskeletal deterioration is proposed. Initially, the abnormal tau protein is distributed diffusely throughout the cell body and the neuronal processes. Subsequently, it aggregates to form a neurofibrillary tangle, which appears as a spherical somatic inclusion. The cell processes gradually become fragmented. Finally the parent cell dies, leaving behind an extraneuronal "ghost tangle". With regard to the cortical stages of AD-related neurofibrillary changes, the initial forms of cytoskeletal changes in the bnM predominate in the transentorhinal AD stages (I and II), while "ghost tangles" preferentially occur in the neocortical stages (V and VI). The considerable morphological diversity of cytoskeletal alterations is typical of stages III and IV. These results indicate that individual neurons of the bnM enter the sequence of cytoskeletal deterioration at different times.     

Effects of various frequency electrical stimulation of the dorsal raphe nucleus on spontaneous firing activities in the rat subthalamic nucleus★

BACKGROUND： Some investigations have demonstrated that exogenous 5-hydroxytryptamine increases the spontaneous firing rate of subthalamic nucleus （STN） neurons in the rat brain. OBJECTIVE： To validate the effect of electrical stimulation to the dorsal raphe nucleus （DRN） on the neuronal activities of the STN in rats, as well as analyze the differences in the effects of electrical stimulation at various frequencies. DESIGN, TIME AND SETTING： Experiments were performed from March 2007 to June 2007 in the Electrophysiology Laboratory of Liaoning Medical University with a randomized controlled animal study design. MATERIALS： Twenty-four healthy male Sprague-Dawley （SD） rats, weighing 250-350 g, were selected for this study. An A320R constant electrical stimulator was purchased from World Precision Instruments Company （USA）; a Spike 2 biological signal acquisition system was purchased from British CED Company. METHODS： Twenty-four SD rats were randomly assigned into a model group and a normal group, with 12 rats in each group. To mimic Parkinson＇s disease, rats in the model group were injected with 4μL of 6-hydroxydopamine into the right striatum, then received deep brain stimulation. Rats in the normal group received deep brain stimulation in same brain region without modeling. Electrical stimulation （width, 0.06 ms; intensity, 0.2-0.6 mA; frequency, 20-130 Hz; train duration, 5 seconds） was delivered to the DRN. MAIN OUTCOME MEASURES： The firing rates of STN neurons were observed by extracellular recording using a biological signal acquisition system. RESULTS： DRN-high-frequency stimulation （DRN-HFS） induced excitation in 59% of the STN neurons in the normal group and 50% of the STN neurons in the model group; mean firing rates increased significantly from （7.14±0.75） and （7.94 ± 0.61） Hz to （11.17 ±1.49） and （12.11 ± 1.05） Hz, respectively （P 〈 0.01）. Spontaneous firing rate increased significantly in 53% of neurons in normal rats in a frequency-dep