An arterially perfused nose-olfactory bulb preparation of the rat

A main feature of the mammalian olfactory bulb network is the presence of various rhythmic activities, in particular, gamma, beta, and theta oscillations, with the latter coupled to the respiratory rhythm. Interactions between those oscillations as well as the spatial distribution of network activation are likely to determine olfactory coding. Here, we describe a novel semi-intact perfused nose-olfactory bulb-brain stem preparation in rats with both a preserved olfactory epithelium and brain stem, which could be particularly suitable for the study of oscillatory activity and spatial odor mapping within the olfactory bulb, in particular, in hitherto inaccessible locations. In the perfused olfactory bulb, we observed robust spontaneous oscillations, mostly in the theta range. Odor application resulted in an increase in oscillatory power in higher frequency ranges, stimulus-locked local field potentials, and excitation or inhibition of individual bulbar neurons, similar to odor responses reported from in vivo recordings. Thus our method constitutes the first viable in situ preparation of a mammalian system that uses airborne odor stimuli and preserves these characteristic features of odor processing. This preparation will allow the use of highly invasive experimental procedures and the application of techniques such as patch-clamp recording, high-resolution imaging, and optogenetics within the entire olfactory bulb.

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Direct Excitation of Mitral Cells Via Activation of α1-Noradrenergic Receptors in Rat Olfactory Bulb Slices

Journal of Neurophysiology ◽

10.1152/jn.2001.86.5.2173 ◽

2001 ◽

Vol 86 (5) ◽

pp. 2173-2182 ◽

Cited By ~ 45

Author(s):

Abdallah Hayar ◽

Phillip M. Heyward ◽

Thomas Heinbockel ◽

Michael T. Shipley ◽

Matthew Ennis

Keyword(s):

Olfactory Bulb ◽

Locus Coeruleus ◽

Equilibrium Potential ◽

Channel Blockers ◽

Mitral Cells ◽

Patch Clamp Recording ◽

Whole Cell ◽

Inward Current

The main olfactory bulb receives a significant modulatory noradrenergic input from the locus coeruleus. Previous in vivo and in vitro studies showed that norepinephrine (NE) inputs increase the sensitivity of mitral cells to weak olfactory inputs. The cellular basis for this action of NE is not understood. The goal of this study was to investigate the effect of NE and noradrenergic agonists on the excitability of mitral cells, the main output cells of the olfactory bulb, using whole cell patch-clamp recording in vitro. The noradrenergic agonists, phenylephrine (PE, 10 μM), isoproterenol (Isop, 10 μM), and clonidine (3 μM), were used to test for the functional presence of α1-, β-, and α2-receptors, respectively, on mitral cells. None of these agonists affected olfactory nerve (ON)–evoked field potentials recorded in the glomerular layer, or ON-evoked postsynaptic currents recorded in mitral cells. In whole cell voltage-clamp recordings, NE (30 μM) induced an inward current (54 ± 7 pA, n= 16) with an EC50 of 4.7 μM. Both PE and Isop also produced inward currents (22 ± 4 pA, n = 19, and 29 ± 9 pA, n = 8, respectively), while clonidine produced no effect ( n = 6). In the presence of TTX (1 μM), and blockers of excitatory and inhibitory fast synaptic transmission [gabazine 5 μM, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) 10 μM, and (±)-2-amino-5-phosphonopentanoic acid (APV) 50 μM], the inward current induced by PE persisted (EC50 = 9 μM), whereas that of Isop was absent. The effect of PE was also observed in the presence of the Ca2+ channel blockers, cadmium (100 μM) and nickel (100 μM). The inward current caused by PE was blocked when the interior of the cell was perfused with the nonhydrolyzable GDP analogue, GDPβS, indicating that the α1 effect is mediated by G-protein coupling. The current-voltage relationship in the absence and presence of PE indicated that the current induced by PE decreased near the equilibrium potential for potassium ions. In current-clamp recordings from bistable mitral cells, PE shifted the membrane potential from the downstate (−52 mV) toward the upstate (−40 mV), and significantly increased spike generation in response to perithreshold ON input. These findings indicate that NE excites mitral cells directly via α1 receptors, an effect that may underlie, at least in part, increased mitral cell responses to weak ON input during locus coeruleus activation in vivo.

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Altered responses of MeCP2-deficient mouse brain stem to severe hypoxia

Journal of Neurophysiology ◽

10.1152/jn.00822.2010 ◽

2011 ◽

Vol 105 (6) ◽

pp. 3067-3079 ◽

Cited By ~ 9

Author(s):

Miriam Kron ◽

Jasper L. Zimmermann ◽

Mathias Dutschmann ◽

Frank Funke ◽

Michael Müller

Keyword(s):

Brain Stem ◽

Respiratory Rhythm ◽

Respiratory Arrest ◽

Wild Type ◽

Cardiorespiratory Control ◽

Breathing Disorders ◽

Life Threatening ◽

Deficient Mice

Rett syndrome (RTT) patients suffer from respiratory arrhythmias with frequent apneas causing intermittent hypoxia. In a RTT mouse model (methyl-CpG-binding protein 2-deficient mice; Mecp2−/ y) we recently discovered an enhanced hippocampal susceptibility to hypoxia and hypoxia-induced spreading depression (HSD). In the present study we investigated whether this also applies to infant Mecp2−/ y brain stem, which could become life-threatening due to failure of cardiorespiratory control. HSD most reliably occurred in the nucleus of the solitary tract (NTS) and the spinal trigeminal nucleus (Sp5). HSD susceptibility of the Mecp2−/ y NTS and Sp5 was increased on 8 mM K+-mediated conditioning. 5-HT1A receptor stimulation with 8-hydroxy-2-(di-propylamino)tetralin (8-OH-DPAT) postponed HSD by up to 40%, mediating genotype-independent protection. The deleterious impact of HSD on in vitro respiration became obvious in rhythmically active slices, where HSD propagation into the pre-Bötzinger complex (pre-BötC) immediately arrested the respiratory rhythm. Compared with wild-type, the Mecp2−/ y pre-BötC was invaded less frequently by HSD, but if so, HSD occurred earlier. On reoxygenation, in vitro rhythms reappeared with increased frequency, which was less pronounced in Mecp2−/ y slices. 8-OH-DPAT increased respiratory frequency but failed to postpone HSD in the pre-BötC. Repetitive hypoxia facilitated posthypoxic recovery only if HSD occurred. In 57% of Mecp2−/ y slices, however, HSD spared the pre-BötC. Although this occasionally promoted residual hypoxic respiratory activity (“gasping”), it also prolonged the posthypoxic recovery, and thus the absence of central inspiratory drive, which in vivo would lengthen respiratory arrest. In view of the breathing disorders in RTTs, the increased hypoxia susceptibility of MeCP2-deficient brain stem potentially contributes to life-threatening disturbances of cardiorespiratory control.

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In vivo beta and gamma subthreshold oscillations in rat mitral cells: origin and gating by respiratory dynamics

Journal of Neurophysiology ◽

10.1152/jn.00053.2017 ◽

2018 ◽

Vol 119 (1) ◽

pp. 274-289 ◽

Cited By ~ 1

Author(s):

Nicolas Fourcaud-Trocmé ◽

Virginie Briffaud ◽

Marc Thévenet ◽

Nathalie Buonviso ◽

Corine Amat

Keyword(s):

Membrane Potential ◽

Olfactory Bulb ◽

Local Field ◽

Local Field Potential ◽

Respiratory Rhythm ◽

Field Potential ◽

Synaptic Activity ◽

Spike Discharge ◽

Subthreshold Oscillations

In mammals, olfactory bulb (OB) dynamics are paced by slow and fast oscillatory rhythms at multiple levels: local field potential, spike discharge, and/or membrane potential oscillations. Interactions between these levels have been well studied for the slow rhythm linked to animal respiration. However, less is known regarding rhythms in the fast beta (10–35 Hz) and gamma (35–100 Hz) frequency ranges, particularly at the membrane potential level. Using a combination of intracellular and extracellular recordings in the OB of freely breathing rats, we show that beta and gamma subthreshold oscillations (STOs) coexist intracellularly and are related to extracellular local field potential (LFP) oscillations in the same frequency range. However, they are differentially affected by changes in cell excitability and by odor stimulation. This leads us to suggest that beta and gamma STOs may rely on distinct mechanisms: gamma STOs would mainly depend on mitral cell intrinsic resonance, while beta STOs could be mainly driven by synaptic activity. In a second study, we find that STO occurrence and timing are constrained by the influence of the slow respiratory rhythm on mitral and tufted cells. First, respiratory-driven excitation seems to favor gamma STOs, while respiratory-driven inhibition favors beta STOs. Second, the respiratory rhythm is needed at the subthreshold level to lock gamma and beta STOs in similar phases as their LFP counterparts and to favor the correlation between STO frequency and spike discharge. Overall, this study helps us to understand how the interaction between slow and fast rhythms at all levels of OB dynamics shapes its functional output. NEW & NOTEWORTHY In the mammalian olfactory bulb of a freely breathing anesthetized rat, we show that both beta and gamma membrane potential fast oscillation ranges exist in the same mitral and tufted (M/T) cell. Importantly, our results suggest they have different origins and that their interaction with the slow subthreshold oscillation (respiratory rhythm) is a key mechanism to organize their dynamics, favoring their functional implication in olfactory bulb information processing.

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Phasic pulmonary stretch receptor feedback modulates both eupnea and gasping in an in situ rat preparation

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00750.2004 ◽

2005 ◽

Vol 289 (2) ◽

pp. R450-R455 ◽

Cited By ~ 6

Author(s):

Michael B. Harris ◽

Walter M. St.-John

Keyword(s):

Brain Stem ◽

Stretch Receptor ◽

Afferent Feedback ◽

Burst Frequency ◽

In Situ Preparation ◽

Stretch Receptors ◽

Pulmonary Stretch Receptors ◽

Pulmonary Stretch Receptor

The perfused in situ juvenile rat preparation produces patterns of phrenic discharge comparable to eupnea and gasping in vivo. These ventilatory patterns differ in multiple aspects, including most prominently the rate of rise of inspiratory activity. Although we have recently demonstrated that both eupnea and gasping are similarly modulated by a Hering-Breuer expiratory-promoting reflex to tonic pulmonary stretch, it has generally been assumed that gasping was unresponsive to afferent stimuli from pulmonary stretch receptors. In the present study, we recorded eupneic and gasplike efferent activity of the phrenic nerve in the in situ juvenile rat perfused brain stem preparation, with and without phrenic-triggered phasic pulmonary inflation. We tested the hypothesis that phasic pulmonary inflation produces reflex responses in situ akin to those in vivo and that both eupnea and gasping are similarly modulated by phasic pulmonary stretch. In eupnea, we found that phasic pulmonary inflation decreases inspiratory burst duration and the period of expiration, thus increasing burst frequency of the phrenic neurogram. Phasic pulmonary inflation also decreases the duration of expiration and increases the burst frequency during gasping. Bilateral vagotomy eliminated these changes. We conclude that the neural substrate mediating the Hering-Breuer reflex is retained in the in situ preparation and that the brain stem circuitry generating the respiratory patterns respond to phasic activation of pulmonary stretch receptors in both eupnea and gasping. These findings support the homology of eupneic phrenic discharge patterns in the reduced in situ preparation and eupnea in vivo and disprove the common supposition that gasping is insensitive to vagal afferent feedback from pulmonary stretch receptor mechanisms.

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Computational model of neurodegenerative damage in the olfactory bulb: role of bulb and damage geometry, damage site, and identification of a potential non-invasive marker of early Parkinson’s disease onset

10.1101/2020.08.06.239293 ◽

2020 ◽

Author(s):

J. Kendall Berry ◽

Daniel L. Cox

Keyword(s):

Parkinson’S Disease ◽

Parkinson's Disease ◽

Olfactory Bulb ◽

Computational Model ◽

Disease Onset ◽

Granule Cell Layer ◽

Oscillatory Activity ◽

Damage Site ◽

Oscillatory Power ◽

The Brain

AbstractThe olfactory bulb (OB) is one of the first regions of the brain affected by Parkinson’s disease (PD) as measured by both dysfunction and presence of α-synuclein aggregation. Better understanding of how PD affects OB function could lead to earlier diagnosis and potential treatment. By simulating damage to the OB in a computational model, it may be possible to identify regions of interest or markers of early disease. We modified a simple rate-based computational model of the olfactory bulb and simulated damage to various components of the network. This was done for several configurations of the network, at different sizes and with 1D and 2D connectivity structures. We found that, in almost every case, activity of 2D networks were more robust to damage than 1D networks, leading us to conclude that a connection scheme of at least 2D is vital to computational modeling of the OB. We also found that certain types of damage (namely, seeded damage to the granule cell layer and to the synapses between mitral and granule cells) resulted in a peak of the oscillatory power of the network as a function of damage. This result is testable experimentally and bears further investigation utilizing more sophisticated computational models. If proven accurate, this rise in oscillatory power in the OB has the potential to be an early marker of PD.Author summaryOne of the first symptoms of Parkinson’s disease is the degradation of the sense of smell. The olfactory bulb is the first region of the brain to process odor information and is affected by Parkinson’s disease at early stages. We simulated neural activity in a computational model of the olfactory bulb in the presence of damage and compared it to simulations of undamaged activity. We found that 2D model networks were more robust to damage than their 1D counterparts. We also found that 2D networks displayed increased oscillatory activity when damage was applied to certain parts of the network. This last result, if proven correct, would potentially be a marker of early-stage Parkinson’s disease, and if so, could aid in early diagnosis and treatment of the disease.

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Late-Expiratory Activity: Emergence and Interactions With the Respiratory CPG

Journal of Neurophysiology ◽

10.1152/jn.00334.2010 ◽

2010 ◽

Vol 104 (5) ◽

pp. 2713-2729 ◽

Cited By ~ 62

Author(s):

Yaroslav I. Molkov ◽

Ana P. L. Abdala ◽

Bartholomew J. Bacak ◽

Jeffrey C. Smith ◽

Julian F. R. Paton ◽

...

Keyword(s):

Computational Model ◽

Brain Stem ◽

Large Scale ◽

Motor Pattern ◽

Respiratory Rhythm ◽

Oscillatory Activity ◽

Published Data ◽

Extended Model ◽

Respiratory Network ◽

Metabolic Conditions

The respiratory rhythm and motor pattern are hypothesized to be generated by a brain stem respiratory network with a rhythmogenic core consisting of neural populations interacting within and between the pre-Bötzinger (pre-BötC) and Bötzinger (BötC) complexes and controlled by drives from other brain stem compartments. Our previous large-scale computational model reproduced the behavior of this network under many different conditions but did not consider neural oscillations that were proposed to emerge within the retrotrapezoid nucleus/parafacial respiratory group (RTN/pFRG) and drive preinspiratory (or late-expiratory, late-E) discharges in the abdominal motor output. Here we extend the analysis of our previously published data and consider new data on the generation of abdominal late-E activity as the basis for extending our computational model. The extended model incorporates an additional late-E population in RTN/pFRG, representing a source of late-E oscillatory activity. In the proposed model, under normal metabolic conditions, this RTN/pFRG oscillator is inhibited by BötC/pre-BötC circuits, and the late-E oscillations can be released by either hypercapnia-evoked activation of RTN/pFRG or by hypoxia-dependent suppression of RTN/pFRG inhibition by BötC/pre-BötC. The proposed interactions between BötC/pre-BötC and RTN/pFRG allow the model to reproduce several experimentally observed behaviors, including quantal acceleration of abdominal late-E oscillations with progressive hypercapnia and quantal slowing of phrenic activity with progressive suppression of pre-BötC excitability, as well as to predict a release of late-E oscillations by disinhibition of RTN/pFRG under normal conditions. The extended model proposes mechanistic explanations for the emergence of RTN/pFRG oscillations and their interaction with the brain stem respiratory network.

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Ultrastructural modification of cellular interactions in cancer tumor

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100082455 ◽

1978 ◽

Vol 36 (2) ◽

pp. 318-319

Author(s):

N. P. Dmitrieva

Keyword(s):

Cancer Cells ◽

Human Thyroid ◽

Adjacent Cell ◽

Main Role ◽

Cellular Interactions ◽

Electron Microscopic ◽

Cancer Tumor ◽

Normal Human ◽

Characteristic Features

One of the most characteristic features of cancer cells is their ability to metastasia. It is suggested that the modifications of the structure and properties of cancer cells surfaces play the main role in this process. The present work was aimed at finding out what ultrastructural features apear in tumor in vivo which removal of individual cancer cells from the cell population can provide. For this purpose the cellular interactions in the normal human thyroid and cancer tumor of this gland electron microscopic were studied. The tissues were fixed in osmium tetroxide and were embedded in Araldite-Epon.In normal human thyroid the most common type of intercellular contacts was represented by simple junction formed by the parallelalignment of adjacent cell membranees leaving in between an intermembranes space 15-20 nm filled with electronlucid material (Fig. 1a). Sometimes in the basal part of cells dilatations of the intercellular space 40-50 nm wide were found (Fig. 1a). Here the cell surfaces may form single short microvilli.

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