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Impact of single-site axonal GABAergic synaptic events on cerebellar interneuron activity.

de San Martin JZ, Jalil A, Trigo FF - J. Gen. Physiol. (2015)

Bottom Line: Axonal ionotropic receptors are present in a variety of neuronal types, and their function has largely been associated with the modulation of axonal activity and synaptic release.The frequency of presynaptic, autoR-mediated miniature currents is twice that of their somatodendritic counterparts, suggesting that autoR-mediated responses have an important effect on interneuron activity.Finally, we show that single-site activation of presynaptic GABA(A) autoRs leads to an increase in MLI excitability and thus conveys a strong feedback signal that contributes to spiking activity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratoire de Physiologie Cérébrale, Université Paris Descartes and Centre National de la Recherche Scientifique, CNRS UMR8118, 75794 Paris, France.

No MeSH data available.


Related in: MedlinePlus

Laser photolysis of caged Ca2+ in axonal varicosities between two connected MLIs evokes simultaneous pre- and postsynaptic currents. (A; left) Fluorescence picture taken with a CCD camera. (Right) Reconstruction of a pair of synaptically connected MLIs. The presynaptic cell is shown in green, and the postsynaptic cell is in magenta. The stimulated site is indicated with the arrowhead in the reconstruction. (B) Simultaneous pre- (top, green) and postsynaptic (bottom, magenta) currents recorded when photolyzing DM-nitrophen with a 100-µs laser pulse. The recordings correspond to individual traces. (C) Latency (left), τrise (middle), and amplitude (right) of pre- (green symbols) and post- (magenta symbols) synaptic currents recorded simultaneously in four different pairs. Open circles correspond to individual experiments, and closed circles correspond to the averages ± SD. Average ± SD values are: pre- and postsynaptic latencies: 1.6 ± 0.4 and 1.6 ± 0.2 ms, respectively; pre- and postsynaptic τrise: 2.8 ± 1.7 and 0.8 ± 0.2 ms, respectively (n = 3 for the presynaptic measurements caused by the difficulties in measuring the τrise in one of the recordings); and pre- and postsynaptic amplitudes: 24 ± 7.7 and 118.5 ± 111 pA, respectively.
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fig1: Laser photolysis of caged Ca2+ in axonal varicosities between two connected MLIs evokes simultaneous pre- and postsynaptic currents. (A; left) Fluorescence picture taken with a CCD camera. (Right) Reconstruction of a pair of synaptically connected MLIs. The presynaptic cell is shown in green, and the postsynaptic cell is in magenta. The stimulated site is indicated with the arrowhead in the reconstruction. (B) Simultaneous pre- (top, green) and postsynaptic (bottom, magenta) currents recorded when photolyzing DM-nitrophen with a 100-µs laser pulse. The recordings correspond to individual traces. (C) Latency (left), τrise (middle), and amplitude (right) of pre- (green symbols) and post- (magenta symbols) synaptic currents recorded simultaneously in four different pairs. Open circles correspond to individual experiments, and closed circles correspond to the averages ± SD. Average ± SD values are: pre- and postsynaptic latencies: 1.6 ± 0.4 and 1.6 ± 0.2 ms, respectively; pre- and postsynaptic τrise: 2.8 ± 1.7 and 0.8 ± 0.2 ms, respectively (n = 3 for the presynaptic measurements caused by the difficulties in measuring the τrise in one of the recordings); and pre- and postsynaptic amplitudes: 24 ± 7.7 and 118.5 ± 111 pA, respectively.

Mentions: MLIs were visualized under a microscope with a 63×/0.9-NA water-dipping objective (Axio Scope; Carl Zeiss) and recorded with the patch technique under the whole-cell configuration, both in voltage and current clamp, with an amplifier (EPC 10; HEKA). The composition of the internal solution (IS) used for the high [Cl−]i experiments was as follows (mM): 90 KCl, 50 HEPES, 0.5 MgCl2, 4.25 CaCl2, 5 Na2ATP, 20 NaCl, 0.5 NaGTP, 25 KOH, 5 1-(2-nitro-4,5-dimethoxyphenyl)-N,N,N′,N′-tetrakis[(oxycarbonyl)methyl]-1,2-ethanediamine (DM-nitrophen), 0.08 Alexa Fluor 488 (or 594 for the experiments in Fig. 1, A and B), and 10 GABA (to avoid washout of intracellular GABA; Bouhours et al., 2011). KCl was replaced by 110 or 100 mM K-gluconate for the experiments with [Cl−]i = 15 and 25 mM, respectively. IS had a pH of 7.3 and an osmolality of ≈300 mOsm kg−1 H2O. Recordings were made at room temperature (22–24°C). In the experiments performed with the low [Cl−]i IS (Figs. 5–7), the membrane potential was corrected for a 12-mV liquid junction potential value (calculated with Patcher’s Power Tools for Igor Pro; F. Mendez and F. Würriehausen, Max-Planck-Institut Für Biophysikalische Chemie, 37077 Göttingen, Germany). Pipette resistance was ∼5 MΩ when filled with the high [Cl−]i IS and ∼10 MΩ when filled with the low [Cl−]i IS. Series resistance was compensated by 50%. Recordings with SR higher than 25 MΩ were discarded. Holding potentials were usually −60 mV. MLI identification was confirmed by the observation of large (0.8–1.7-nA), unclamped Na+ currents when the membrane potential was stepped from −60 to 0 mV for 2 ms (Pouzat and Marty, 1999). Recordings were filtered at 5 kHz with a Bessel filter. Data were analyzed using routines written in Igor Pro (WaveMetrics). Most data were obtained from cells located in the proximal part of the molecular layer (basket cells); however, interneurons located in the distal molecular layer (stellate cells) were also included. Reagents were purchased from Sigma-Aldrich, and gabazine (Gbz) and tetrodotoxin (TTX) were from Abcam.


Impact of single-site axonal GABAergic synaptic events on cerebellar interneuron activity.

de San Martin JZ, Jalil A, Trigo FF - J. Gen. Physiol. (2015)

Laser photolysis of caged Ca2+ in axonal varicosities between two connected MLIs evokes simultaneous pre- and postsynaptic currents. (A; left) Fluorescence picture taken with a CCD camera. (Right) Reconstruction of a pair of synaptically connected MLIs. The presynaptic cell is shown in green, and the postsynaptic cell is in magenta. The stimulated site is indicated with the arrowhead in the reconstruction. (B) Simultaneous pre- (top, green) and postsynaptic (bottom, magenta) currents recorded when photolyzing DM-nitrophen with a 100-µs laser pulse. The recordings correspond to individual traces. (C) Latency (left), τrise (middle), and amplitude (right) of pre- (green symbols) and post- (magenta symbols) synaptic currents recorded simultaneously in four different pairs. Open circles correspond to individual experiments, and closed circles correspond to the averages ± SD. Average ± SD values are: pre- and postsynaptic latencies: 1.6 ± 0.4 and 1.6 ± 0.2 ms, respectively; pre- and postsynaptic τrise: 2.8 ± 1.7 and 0.8 ± 0.2 ms, respectively (n = 3 for the presynaptic measurements caused by the difficulties in measuring the τrise in one of the recordings); and pre- and postsynaptic amplitudes: 24 ± 7.7 and 118.5 ± 111 pA, respectively.
© Copyright Policy - openaccess
Related In: Results  -  Collection

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fig1: Laser photolysis of caged Ca2+ in axonal varicosities between two connected MLIs evokes simultaneous pre- and postsynaptic currents. (A; left) Fluorescence picture taken with a CCD camera. (Right) Reconstruction of a pair of synaptically connected MLIs. The presynaptic cell is shown in green, and the postsynaptic cell is in magenta. The stimulated site is indicated with the arrowhead in the reconstruction. (B) Simultaneous pre- (top, green) and postsynaptic (bottom, magenta) currents recorded when photolyzing DM-nitrophen with a 100-µs laser pulse. The recordings correspond to individual traces. (C) Latency (left), τrise (middle), and amplitude (right) of pre- (green symbols) and post- (magenta symbols) synaptic currents recorded simultaneously in four different pairs. Open circles correspond to individual experiments, and closed circles correspond to the averages ± SD. Average ± SD values are: pre- and postsynaptic latencies: 1.6 ± 0.4 and 1.6 ± 0.2 ms, respectively; pre- and postsynaptic τrise: 2.8 ± 1.7 and 0.8 ± 0.2 ms, respectively (n = 3 for the presynaptic measurements caused by the difficulties in measuring the τrise in one of the recordings); and pre- and postsynaptic amplitudes: 24 ± 7.7 and 118.5 ± 111 pA, respectively.
Mentions: MLIs were visualized under a microscope with a 63×/0.9-NA water-dipping objective (Axio Scope; Carl Zeiss) and recorded with the patch technique under the whole-cell configuration, both in voltage and current clamp, with an amplifier (EPC 10; HEKA). The composition of the internal solution (IS) used for the high [Cl−]i experiments was as follows (mM): 90 KCl, 50 HEPES, 0.5 MgCl2, 4.25 CaCl2, 5 Na2ATP, 20 NaCl, 0.5 NaGTP, 25 KOH, 5 1-(2-nitro-4,5-dimethoxyphenyl)-N,N,N′,N′-tetrakis[(oxycarbonyl)methyl]-1,2-ethanediamine (DM-nitrophen), 0.08 Alexa Fluor 488 (or 594 for the experiments in Fig. 1, A and B), and 10 GABA (to avoid washout of intracellular GABA; Bouhours et al., 2011). KCl was replaced by 110 or 100 mM K-gluconate for the experiments with [Cl−]i = 15 and 25 mM, respectively. IS had a pH of 7.3 and an osmolality of ≈300 mOsm kg−1 H2O. Recordings were made at room temperature (22–24°C). In the experiments performed with the low [Cl−]i IS (Figs. 5–7), the membrane potential was corrected for a 12-mV liquid junction potential value (calculated with Patcher’s Power Tools for Igor Pro; F. Mendez and F. Würriehausen, Max-Planck-Institut Für Biophysikalische Chemie, 37077 Göttingen, Germany). Pipette resistance was ∼5 MΩ when filled with the high [Cl−]i IS and ∼10 MΩ when filled with the low [Cl−]i IS. Series resistance was compensated by 50%. Recordings with SR higher than 25 MΩ were discarded. Holding potentials were usually −60 mV. MLI identification was confirmed by the observation of large (0.8–1.7-nA), unclamped Na+ currents when the membrane potential was stepped from −60 to 0 mV for 2 ms (Pouzat and Marty, 1999). Recordings were filtered at 5 kHz with a Bessel filter. Data were analyzed using routines written in Igor Pro (WaveMetrics). Most data were obtained from cells located in the proximal part of the molecular layer (basket cells); however, interneurons located in the distal molecular layer (stellate cells) were also included. Reagents were purchased from Sigma-Aldrich, and gabazine (Gbz) and tetrodotoxin (TTX) were from Abcam.

Bottom Line: Axonal ionotropic receptors are present in a variety of neuronal types, and their function has largely been associated with the modulation of axonal activity and synaptic release.The frequency of presynaptic, autoR-mediated miniature currents is twice that of their somatodendritic counterparts, suggesting that autoR-mediated responses have an important effect on interneuron activity.Finally, we show that single-site activation of presynaptic GABA(A) autoRs leads to an increase in MLI excitability and thus conveys a strong feedback signal that contributes to spiking activity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratoire de Physiologie Cérébrale, Université Paris Descartes and Centre National de la Recherche Scientifique, CNRS UMR8118, 75794 Paris, France.

No MeSH data available.


Related in: MedlinePlus