Effect of H+ on the membrane potential of silent cells in the ventral and dorsal surface layers of the rat medulla in vitro

Fukuda, Yasuichiro; Honda, Yoshiyuki; Schläfke, Marianne E.; Loeschcke, H. H.

doi:10.1007/bf00584955

Cited by 60 publications

(39 citation statements)

References 31 publications

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“…However, the control of phasic firing, which is commonly found during osmotic excitation, would seem to involve a mechanism which lies within or in close proximity to, the neurosecretory neurones. INTRODUCTION The technique of incubating brain slices in vitro has been used for electrophysiological experiments on a variety of different structures, including the olfactory cortex (Yamomoto & Mcllwain, 1966;Richards & Sercombe, 1970;Scholfield, 1978), hippocampus (Skrede & Westgaard, 1971;Schwartzkroin, 1975) and medulla (Fukuda, Honda, Schlafke & Loescheke, 1978). Preparations in vitro make it possible to study neuronal systems in functional isolation from the rest of the brain, facilitate manipulation of their extracellular envrionment, and obviate the necessity for anaesthetic or immobilizing agents to obtain stable recording conditions.…”

Section: One Hundred and Two Pv And So Units Incubated In Hypertomentioning

confidence: 99%

Electrophysiological studies of paraventricular and supraoptic neurones recorded in vitro from slices of rat hypothalamus.

Haller¹,

Wakerley²

1980

The Journal of Physiology

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SUMMARY1. In slices (300 stm) of rat hypothalamus maintained in vitro in isotonic (298 + 4 m-osmol/kg) medium, the median firing rate of twenty-four supraoptic (s.o.) neurones was 0.05 spikes/s, compared to 0-66 spikes/s for twenty-eight paraventricular (p.v.) 4. Mean durations of bursts and silent periods in phasic cells excited by perifused glutamate were 16-6 s and 13-2 s (calculated from normalized distributions of thirty values), compared to means of 41-7 s and 33-9 s (thirty-six values, P < 0-001 for each parameter) for cells excited by glutamate ionophoresis. The periodicity of phasic firing in vitro was unaffected by a change to hypertonic (340 m-osmol/kg) medium.5. From these in vitro results it is proposed that the excitation associated with osmotic stimuli in vivo does not originate within the p.v. and s.o. neurosecretory cells, but that it involves a separate osmoreceptor. However, the control of phasic firing, which is commonly found during osmotic excitation, would seem to involve a mechanism which lies within or in close proximity to, the neurosecretory neurones.

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Section: One Hundred and Two Pv And So Units Incubated In Hypertomentioning

confidence: 99%

Electrophysiological studies of paraventricular and supraoptic neurones recorded in vitro from slices of rat hypothalamus.

Haller¹,

Wakerley²

1980

The Journal of Physiology

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“…In their "resting" state microglia can interact with all elements of the CNS and can respond to a variety of physiological signals, including pH (13). However, microglia have a resting membrane potential (approximately Ϫ40 mV) that is considerably more depolarized than the resting membrane potential of pH-sensitive glia (approximately Ϫ70 mV) (16,53), suggesting that pH-sensitive RTN glia are probably not microglia. Other characteristics of resting microglia include high membrane resistance and the presence of inward rectifying K ϩ (Kir) channels, ␣-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors, and glutamate transporters (3,55).…”

Section: General Characteristics Of Glial Cellsmentioning

confidence: 99%

“…In a similar fashion, RTN glia may also contribute to chemoreception by modulating activity of pH-sensitive RTN neurons. For example, the RTN also contains pH-sensitive glial cells (12,16,53). Since tetrodotoxin will not inhibit glial transmitter release, it remains possible that local paracrine mechanisms, including excitatory input from pH-sensitive glial cells, could contribute to pH sensitivity of RTN neurons and respiratory drive.…”

Section: The Rtn Is An Important Site Of Central Chemoreceptionmentioning

confidence: 99%

“…1 for more details). The RTN also contains a population of pH-sensitive glial cells (12,16,53) that may contribute to chemoreception by releasing ATP during hypercapnia. Evidence indicates that ATP can contribute to chemoreception by 1) activating pH-sensitive neurons through a P2Y-receptor-dependent mechanism (arrow 1); 2) inhibiting pH-sensitive neurons by activation of P2X-receptors on interneurons (arrow 2); 3) modulating vascular tone to increase or decrease tissue pH (arrow 3).…”

Section: The Rtn Is An Important Site Of Central Chemoreceptionmentioning

confidence: 99%

“…In this review, we will summarize the properties of chemosensitive RTN neurons; further details on this topic can be found in several recent reviews (23,24,41). Surprisingly, pH-sensitive RTN glial cells, first described by Fukuda et al (16) more than 30 years ago, have received relatively little attention (9 -11, 46, 53) despite evidence from other brain regions that glial cells can function as important modulators of both neural network activity and vascular tone (25). Therefore, we will also describe general characteristics of glial cells and propose an expanded model of chemoreception that includes a role for RTN glia as a source of excitatory drive to pHsensitive neurons as well as a regulator of local vascular tone.…”

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Current ideas on central chemoreception by neurons and glial cells in the retrotrapezoid nucleus

Mulkey

Wenker

Kréneisz

2010

Journal of Applied Physiology

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(23), and recent evidence suggests that RTN chemoreception involves two interrelated mechanisms: H ϩ -mediated activation of pH-sensitive neurons (38) and purinergic signaling (19), possibly from pH-sensitive glial cells. A third, potentially important, aspect of RTN chemoreception is the regulation of blood flow, which is an important determinate of tissue pH and consequently chemoreceptor activity. It is well established in vivo that changes in cerebral blood flow can profoundly affect the chemoreflex (2); e.g., limiting blood flow by vasoconstriction acidifies tissue pH and increases the ventilatory response to CO 2, whereas vasodilation can wash out metabolically produced CO2 from tissue to increase tissue pH and decrease the stimulus at chemoreceptors. In this review, we will summarize the defining characteristics of pH-sensitive neurons and discuss potential contributions of pH-sensitive glial cells as both a source of purinergic drive to pH-sensitive neurons and a modulator of vasculature tone.control of breathing; central chemoreceptor; vascular control; neural-glial interactions CENTRAL CHEMORECEPTION IS the mechanism by which the brain regulates breathing in response to changes in tissue pH, wherein CO 2 /H ϩ chemoreceptors sense pH changes to regulate the depth and frequency of breathing. Several brain regions are thought to participate in chemoreception including the nucleus tractus solitarius, locus coeruleus, medullary raphe, prebotzinger complex, fastigial nucleus of the cerebellum, hypothalamus, and retrotrapezoid nucleus (RTN) (14,22). Although the relative contributions of these putative chemoreceptor regions remains controversial (24, 42), there is compelling evidence that the RTN is an important site of chemoreception (1,6,26,38,43). In this review, we will summarize the properties of chemosensitive RTN neurons; further details on this topic can be found in several recent reviews (23,24,41). Surprisingly, pH-sensitive RTN glial cells, first described by Fukuda et al.(16) more than 30 years ago, have received relatively little attention (9 -11, 46, 53) despite evidence from other brain regions that glial cells can function as important modulators of both neural network activity and vascular tone (25). Therefore, we will also describe general characteristics of glial cells and propose an expanded model of chemoreception that includes a role for RTN glia as a source of excitatory drive to pHsensitive neurons as well as a regulator of local vascular tone. THE RTN IS AN IMPORTANT SITE OF CENTRAL CHEMORECEPTIONThe early work of Mitchell and colleagues more than 40 years ago established that acidification of the ventral medullary surface (area M) stimulates breathing (34); therefore, they concluded that pH-sensitive neurons in this region, later defined as the RTN (57), are able to provide the chemical drive to breathe. This possibility has been strengthened by a series of in vivo experiments by Nattie and colleagues who showed that chemical activation of the RTN led to increased respiratory drive...

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Central respiratory chemoreception

Guyenet¹,

Stornetta²,

Bayliss³

2010

J of Comparative Neurology

213

187

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Summary By definition central respiratory chemoreceptors (CRCs) are cells that are sensitive to changes in brain PCO2 or pH and contribute to the stimulation of breathing elicited by hypercapnia or metabolic acidosis. CO2 most likely works by lowering pH. The pertinent proton receptors have not been identified and may be ion channels. CRCs are probably neurons but may also include acid-sensitive glia and vascular cells that communicate with neurons via paracrine mechanisms. Retrotrapezoid nucleus (RTN) neurons are the most completely characterized CRCs. Their high sensitivity to CO2 in vivo presumably relies on their intrinsic acid-sensitivity, excitatory inputs from the carotid bodies and brain regions such as raphe and hypothalamus, and facilitating influences from neighboring astrocytes. RTN neurons are necessary for the respiratory network to respond to CO2 during the perinatal period and under anesthesia. In conscious adults, RTN neurons contribute to an unknown degree to the pH-dependent regulation of breathing rate, inspiratory and expiratory activity. The abnormal prenatal development of RTN neurons probably contributes to the congenital central hypoventilation syndrome. Other CRCs presumably exist but the supportive evidence is less complete. The proposed locations of these CRCs are the medullary raphe, the nucleus tractus solitarius, the ventrolateral medulla, the fastigial nucleus and the hypothalamus. Several wake-promoting systems (serotonergic and catecholaminergic neurons, orexinergic neurons) are also putative CRCs. Their contribution to central respiratory chemoreception may be behavior-dependent or vary according to the state of vigilance.

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Effect of H+ on the membrane potential of silent cells in the ventral and dorsal surface layers of the rat medulla in vitro

Cited by 60 publications

References 31 publications

Electrophysiological studies of paraventricular and supraoptic neurones recorded in vitro from slices of rat hypothalamus.

Electrophysiological studies of paraventricular and supraoptic neurones recorded in vitro from slices of rat hypothalamus.

Current ideas on central chemoreception by neurons and glial cells in the retrotrapezoid nucleus

Central respiratory chemoreception

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