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Glycinergic interneurons are functionally integrated into the inspiratory network of mouse medullary slices.

Winter SM, Fresemann J, Schnell C, Oku Y, Hirrlinger J, Hülsmann S - Pflugers Arch. (2009)

Bottom Line: Inspiratory (96%) and 'tonic' expiratory neurons (4%) were identified via an increase or decrease, respectively, of the cytosolic free calcium concentration during the inspiratory-related respiratory burst.We also found glycinergic neurons that receive phasic inhibition from other glycinergic neurons.Our calcium imaging data show that glycinergic neurons comprise a large population of inspiratory neurons in the pre-Bötzinger complex-driven network of the rhythmic slice preparation.

View Article: PubMed Central - PubMed

Affiliation: Abt Neuro- und Sinnesphysiologie, Zentrum Physiologie und Pathophysiologie, Georg-August-Universität, Göttingen, Germany.

ABSTRACT
Neuronal activity in the respiratory network is functionally dependent on inhibitory synaptic transmission. Using two-photon excitation microscopy, we analyzed the integration of glycinergic neurons in the isolated inspiratory pre-Bötzinger complex-driven network of the rhythmic slice preparation. Inspiratory (96%) and 'tonic' expiratory neurons (4%) were identified via an increase or decrease, respectively, of the cytosolic free calcium concentration during the inspiratory-related respiratory burst. Furthermore, in BAC-transgenic mice expressing EGFP under the control of the GlyT2-promoter, 50% of calcium-imaged inspiratory neurons were glycinergic. Inspiratory bursting of glycinergic neurons in the slice was confirmed by whole-cell recording. We also found glycinergic neurons that receive phasic inhibition from other glycinergic neurons. Our calcium imaging data show that glycinergic neurons comprise a large population of inspiratory neurons in the pre-Bötzinger complex-driven network of the rhythmic slice preparation.

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a CCD camera image of the EGFP-expression of a glycinergic neuron recorded in b (epifluorescence, excitation using 467 nm). b Current clamp recording of the glycinergic neuron (in a) showing tonic spike activity without rhythmic modulation (∫ integral of the population field potential). c–e Example of a glycinergic neuron (c) that receives phasic excitatory input. d Current clamp recording showing tonic activity with a phasic increase of action potential frequency. e Injection of negative current (−40 pA) results in a cessation of tonic activity and uncovers bursts of action potentials resulting from phasic excitation. f, g Glycinergic neuron (f) showing a phasic reduction of action potential frequency, the typical behavior of a tonic expiratory neuron (g)
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Fig4: a CCD camera image of the EGFP-expression of a glycinergic neuron recorded in b (epifluorescence, excitation using 467 nm). b Current clamp recording of the glycinergic neuron (in a) showing tonic spike activity without rhythmic modulation (∫ integral of the population field potential). c–e Example of a glycinergic neuron (c) that receives phasic excitatory input. d Current clamp recording showing tonic activity with a phasic increase of action potential frequency. e Injection of negative current (−40 pA) results in a cessation of tonic activity and uncovers bursts of action potentials resulting from phasic excitation. f, g Glycinergic neuron (f) showing a phasic reduction of action potential frequency, the typical behavior of a tonic expiratory neuron (g)

Mentions: To further analyze the integration of glycinergic neurons in the preBötC-driven network, we conducted whole-cell current clamp recordings from EGFP-labeled cells. Approximately, 50% of the glycinergic neurons showed a tonic firing pattern (28/54 glycinergic neurons; Fig. 4a, b). Consistent with our two-photon imaging data, we found glycinergic neurons that received excitatory synaptic inputs in phase with the preBötC-driven field potential burst (n = 8; Fig. 4c–e). These excitatory inputs were capable to produce a phasic increase of action potential frequency in four glycinergic neurons (Fig. 4d). Injection of steady hyperpolarizing current resulted in periodic bursts of action potentials that were in synchrony with the field potential (Fig. 4e). One labeled glycinergic neuron, by contrast, exhibited periodic inhibition of discharge that was time-locked to the population field potential.Fig. 4


Glycinergic interneurons are functionally integrated into the inspiratory network of mouse medullary slices.

Winter SM, Fresemann J, Schnell C, Oku Y, Hirrlinger J, Hülsmann S - Pflugers Arch. (2009)

a CCD camera image of the EGFP-expression of a glycinergic neuron recorded in b (epifluorescence, excitation using 467 nm). b Current clamp recording of the glycinergic neuron (in a) showing tonic spike activity without rhythmic modulation (∫ integral of the population field potential). c–e Example of a glycinergic neuron (c) that receives phasic excitatory input. d Current clamp recording showing tonic activity with a phasic increase of action potential frequency. e Injection of negative current (−40 pA) results in a cessation of tonic activity and uncovers bursts of action potentials resulting from phasic excitation. f, g Glycinergic neuron (f) showing a phasic reduction of action potential frequency, the typical behavior of a tonic expiratory neuron (g)
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2691554&req=5

Fig4: a CCD camera image of the EGFP-expression of a glycinergic neuron recorded in b (epifluorescence, excitation using 467 nm). b Current clamp recording of the glycinergic neuron (in a) showing tonic spike activity without rhythmic modulation (∫ integral of the population field potential). c–e Example of a glycinergic neuron (c) that receives phasic excitatory input. d Current clamp recording showing tonic activity with a phasic increase of action potential frequency. e Injection of negative current (−40 pA) results in a cessation of tonic activity and uncovers bursts of action potentials resulting from phasic excitation. f, g Glycinergic neuron (f) showing a phasic reduction of action potential frequency, the typical behavior of a tonic expiratory neuron (g)
Mentions: To further analyze the integration of glycinergic neurons in the preBötC-driven network, we conducted whole-cell current clamp recordings from EGFP-labeled cells. Approximately, 50% of the glycinergic neurons showed a tonic firing pattern (28/54 glycinergic neurons; Fig. 4a, b). Consistent with our two-photon imaging data, we found glycinergic neurons that received excitatory synaptic inputs in phase with the preBötC-driven field potential burst (n = 8; Fig. 4c–e). These excitatory inputs were capable to produce a phasic increase of action potential frequency in four glycinergic neurons (Fig. 4d). Injection of steady hyperpolarizing current resulted in periodic bursts of action potentials that were in synchrony with the field potential (Fig. 4e). One labeled glycinergic neuron, by contrast, exhibited periodic inhibition of discharge that was time-locked to the population field potential.Fig. 4

Bottom Line: Inspiratory (96%) and 'tonic' expiratory neurons (4%) were identified via an increase or decrease, respectively, of the cytosolic free calcium concentration during the inspiratory-related respiratory burst.We also found glycinergic neurons that receive phasic inhibition from other glycinergic neurons.Our calcium imaging data show that glycinergic neurons comprise a large population of inspiratory neurons in the pre-Bötzinger complex-driven network of the rhythmic slice preparation.

View Article: PubMed Central - PubMed

Affiliation: Abt Neuro- und Sinnesphysiologie, Zentrum Physiologie und Pathophysiologie, Georg-August-Universität, Göttingen, Germany.

ABSTRACT
Neuronal activity in the respiratory network is functionally dependent on inhibitory synaptic transmission. Using two-photon excitation microscopy, we analyzed the integration of glycinergic neurons in the isolated inspiratory pre-Bötzinger complex-driven network of the rhythmic slice preparation. Inspiratory (96%) and 'tonic' expiratory neurons (4%) were identified via an increase or decrease, respectively, of the cytosolic free calcium concentration during the inspiratory-related respiratory burst. Furthermore, in BAC-transgenic mice expressing EGFP under the control of the GlyT2-promoter, 50% of calcium-imaged inspiratory neurons were glycinergic. Inspiratory bursting of glycinergic neurons in the slice was confirmed by whole-cell recording. We also found glycinergic neurons that receive phasic inhibition from other glycinergic neurons. Our calcium imaging data show that glycinergic neurons comprise a large population of inspiratory neurons in the pre-Bötzinger complex-driven network of the rhythmic slice preparation.

Show MeSH
Related in: MedlinePlus