Effects of extracellular calcium and magnesium on central respiratory control in the brainstem–spinal cord of neonatal rat

Kuwana, Shun-ichi; Okada, Yasumasa; Natsui, Teijiro

doi:10.1016/s0006-8993(97)01476-5

Cited by 31 publications

(17 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[Ca 2ϩ ] o may show significant fluctuations in association with physiological neuronal activity (Somjen and Giacchino, 1985;Massimini and Amzica, 2001). Conversely, changes in extracellular divalent cations may have dramatic effects on physiological neuronal function (Kuwana et al, 1998;Hsu et al, 2000). The concentrations of extracellular divalent cations have also been shown to undergo large changes in association with pathological states such as ischemia, hypoglycemia, or seizures (Harris and Symon, 1984;Somjen and Giacchino, 1985;Silver and Erecinska, 1990;Zhang et al, 1990;Kristian et al, 1993;Altura et al, 1997;Szilagyi et al, 2000).…”

Section: Discussionmentioning

confidence: 99%

Modulation of intercellular calcium signaling in astrocytes by extracellular calcium and magnesium

Stout

Charles

2003

Glia

View full text Add to dashboard Cite

The extracellular concentrations of Ca 2ϩ and Mg 2ϩ are well known to play important roles in the function of the central nervous system. We examined the effects of extracellular Ca 2ϩ and Mg 2ϩ on ATP release and intercellular signaling in astrocytes. [Ca 2ϩ ] o -activated whole cell currents consistent with currents through connexin hemichannels. These currents were inhibited by extracellular Mg 2ϩ . We conclude that extracellular divalent cations modulate intercellular Ca 2ϩ signaling in astrocytes by modulating the release of ATP, possibly via connexin hemichannels.

show abstract

Section: Discussionmentioning

confidence: 99%

Modulation of intercellular calcium signaling in astrocytes by extracellular calcium and magnesium

Stout

Charles

2003

Glia

View full text Add to dashboard Cite

show abstract

“…A number of studies have indicated that Ca 2ϩ may play a role in chemosensitive signaling. An increase in extracellular Ca 2ϩ has been shown to decrease the integrated respiratory output in the brain stem-spinal cord preparation and also to reduce the response to hypercapnia (197). However, it is not clear whether this effect is on central chemosensors or on the rhythm generator.…”

Section: Other Factors In Central Chemosensitive Signalingmentioning

confidence: 99%

Cellular mechanisms involved in CO₂ and acid signaling in chemosensitive neurons

Putnam

Filosa

Ritucci

2004

American Journal of Physiology-Cell Physiology

277

343

View full text Add to dashboard Cite

An increase in CO(2)/H(+) is a major stimulus for increased ventilation and is sensed by specialized brain stem neurons called central chemosensitive neurons. These neurons appear to be spread among numerous brain stem regions, and neurons from different regions have different levels of chemosensitivity. Early studies implicated changes of pH as playing a role in chemosensitive signaling, most likely by inhibiting a K(+) channel, depolarizing chemosensitive neurons, and thereby increasing their firing rate. Considerable progress has been made over the past decade in understanding the cellular mechanisms of chemosensitive signaling using reduced preparations. Recent evidence has pointed to an important role of changes of intracellular pH in the response of central chemosensitive neurons to increased CO(2)/H(+) levels. The signaling mechanisms for chemosensitivity may also involve changes of extracellular pH, intracellular Ca(2+), gap junctions, oxidative stress, glial cells, bicarbonate, CO(2), and neurotransmitters. The normal target for these signals is generally believed to be a K(+) channel, although it is likely that many K(+) channels as well as Ca(2+) channels are involved as targets of chemosensitive signals. The results of studies of cellular signaling in central chemosensitive neurons are compared with results in other CO(2)- and/or H(+)-sensitive cells, including peripheral chemoreceptors (carotid body glomus cells), invertebrate central chemoreceptors, avian intrapulmonary chemoreceptors, acid-sensitive taste receptor cells on the tongue, and pain-sensitive nociceptors. A multiple factors model is proposed for central chemosensitive neurons in which multiple signals that affect multiple ion channel targets result in the final neuronal response to changes in CO(2)/H(+).

show abstract

“…However, perfusion with nominally Ca 2+ -free ACSF does not guarantee that the concentration of extracellular Ca 2+ in the spinal cord is sufficiently low to block synaptic transmission (Kuwana et al 1998;Piccolino et al 1998). Moreover, low Ca 2+ ion concentration alone may actually increase neuronal excitability by reducing the surface-charge screening effect that Ca 2+ ions exert on the negatively charged external surface of cell membranes (for review see Piccolino et al 1998).…”

Section: Camentioning

confidence: 99%

“…Thus, in the present study, addition of EGTA enabled blockade of locomotor-like activity elicited by supra-threshold levels of electrical stimulation, whereas Ca 2+ -free ACSF alone did not. Alternatively, elevation of extracellular Mg 2+ ion concentration was used to suppress neurotransmitter release (Katz & Miledi, 1963;Kuno & Takahashi, 1986;Czeh & Somjen, 1989;Lev-Tov & Pinco, 1992;Kuwana et al 1998). Mg 2+ ions also restore the membrane surface-charge screening effect that is lost when Ca 2+ ions are removed from ACSF, thereby preventing increased membrane excitability in low Ca 2+ solutions (for review see Bernath, 1992).…”

Section: Camentioning

confidence: 99%

Propriospinal neurons contribute to bulbospinal transmission of the locomotor command signal in the neonatal rat spinal cord

Zaporozhets

Cowley

Schmidt

2006

The Journal of Physiology

View full text Add to dashboard Cite

This study examines whether propriospinal transmission contributes to descending propagation of the brainstem locomotor command signal in the in vitro neonatal rat spinal cord. Using double bath partitions, synaptic transmission was suppressed in the cervicothoracic region while monitoring locomotor-like activity on lumbar ventral roots evoked by either chemical or electrical stimulation of the brainstem. Locomotor-like activity induced by electrical stimulation was more stable (cycle period coefficient of variation (CV) 11.7 ± 6.1%) than the rhythm induced by chemical stimulation (CV 31.3 ± 6.4%). Ca 2+ -free bath solution, elevated Mg 2+ ion concentration, excitatory amino acid receptor antagonists (AP5 and/or CNQX), and the muscarinic receptor antagonist, atropine, were used in attempts to block synaptic transmission. Each of these manipulations, except muscarinic receptor blockade, was capable of blocking locomotor-like activity induced by brainstem stimulation. However, locomotor-like activity induced by higher intensity electrical stimulation of the brainstem (1.2-5 times threshold) was relatively refractory to synaptic suppression using AP5 and CNQX, and Ca 2+ -free solution was more effective if combined with high Mg 2+ (15 mM) or EGTA. Enhancement of neuronal excitation in the cervicothoracic region, using Mg 2+ -free bath solution, facilitated brainstem activation of locomotor-like activity in the lumbar cord, consistent with a propriospinal mechanism of locomotor signal propagation. Blockade of brainstem-induced locomotor-like activity was related to the number of cervicothoracic segments exposed to synaptic suppression, being most effective if five or more segments were included. These results provide direct evidence that propriospinal pathways contribute to bulbospinal activation of the locomotor network in the in vitro neonatal rat brainstem-spinal cord preparation, and suggest that a propriospinal system is recruited in parallel with long direct projections that activate the locomotor network. Development of successful spinal cord repair strategies demands an understanding of the anatomical and physiological substrates of normal functions such as locomotion. Two well-established features of the mammalian locomotor pattern-generating network are that components of this circuitry can remain relatively intact in spinal cord segments caudal to the site of injury and the network can be activated by relatively simple unmodulated excitatory input. Thus, an important and realistic challenge for spinal cord research is to devise methods of re-establishing supraspinal input to locomotor rhythm-generating elements located caudal to spinal cord injury. A major obstacle in achieving this goal is the lack of identification and characterization of descending locomotor command pathways. Another impediment is the limited capacity of axons to regenerate over long distances in the central nervous system. On the other hand, if it could be shown that locomotor command signals are relayed through a polysynaptic network...

show abstract

Effects of extracellular calcium and magnesium on central respiratory control in the brainstem–spinal cord of neonatal rat

Cited by 31 publications

References 37 publications

Modulation of intercellular calcium signaling in astrocytes by extracellular calcium and magnesium

Modulation of intercellular calcium signaling in astrocytes by extracellular calcium and magnesium

Cellular mechanisms involved in CO₂ and acid signaling in chemosensitive neurons

Propriospinal neurons contribute to bulbospinal transmission of the locomotor command signal in the neonatal rat spinal cord

Contact Info

Product

Resources

About

Effects of extracellular calcium and magnesium on central respiratory control in the brainstem–spinal cord of neonatal rat

Cited by 31 publications

References 37 publications

Modulation of intercellular calcium signaling in astrocytes by extracellular calcium and magnesium

Modulation of intercellular calcium signaling in astrocytes by extracellular calcium and magnesium

Cellular mechanisms involved in CO2 and acid signaling in chemosensitive neurons

Propriospinal neurons contribute to bulbospinal transmission of the locomotor command signal in the neonatal rat spinal cord

Contact Info

Product

Resources

About

Cellular mechanisms involved in CO₂ and acid signaling in chemosensitive neurons