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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

AutoR-mediated responses are amplified by activation of Nav channels. (A) Representative traces of average laser-evoked ASPs in control (black) and in TTX (gray; 400 nM). Summary plot of TTX effect on (B) ASP amplitude (control: 3.1 ± 1 mV; TTX: 1.9 ± 1 mV; paired t test, **, P < 0.01; n = 7 sites), (C) τRise (control: 13 ± 4 ms; TTX: 9 ± 4 ms; paired t test, **, P < 0.01; n = 7 sites), and (D) τDecay (control: 145 ± 88 ms; TTX: 75 ± 48 ms; paired t test, *, P < 0.05; n = 7 sites). Black dots represent mean ± SEM.
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fig8: AutoR-mediated responses are amplified by activation of Nav channels. (A) Representative traces of average laser-evoked ASPs in control (black) and in TTX (gray; 400 nM). Summary plot of TTX effect on (B) ASP amplitude (control: 3.1 ± 1 mV; TTX: 1.9 ± 1 mV; paired t test, **, P < 0.01; n = 7 sites), (C) τRise (control: 13 ± 4 ms; TTX: 9 ± 4 ms; paired t test, **, P < 0.01; n = 7 sites), and (D) τDecay (control: 145 ± 88 ms; TTX: 75 ± 48 ms; paired t test, *, P < 0.05; n = 7 sites). Black dots represent mean ± SEM.

Mentions: Upon photolysis of DM-nitrophen, two net OH ions are formed per molecule of Ca2+ DM-nitrophen photolyzed. To buffer this pH change, 50 mM HEPES was used (see composition of IS above). Even with this high HEPES concentration, a pH change of ≈0.37 pH units is expected; in similar experimental conditions, this pH change had no effect on synaptic transmission (Trigo et al., 2012). The number of repetitions that can be performed when intracellularly photolyzing DM-nitrophen is limited. In this work, the maximum number of repetitions were 12 and 22 with high and low [Cl−]i solutions, respectively. This is not caused by direct photodamage with the 405-nm laser because it is not observed when photolyzing other caged compounds in the extracellular milieu, like glutamate or GABA, with the same method (Trigo et al., 2009b; this work, Fig. 8); rather, it may be caused by the release of oxidizing subproducts (nitrosoacetophenone; Kaplan and Ellis-Davies, 1988), but the exact mechanisms remain to be explored.


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

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

AutoR-mediated responses are amplified by activation of Nav channels. (A) Representative traces of average laser-evoked ASPs in control (black) and in TTX (gray; 400 nM). Summary plot of TTX effect on (B) ASP amplitude (control: 3.1 ± 1 mV; TTX: 1.9 ± 1 mV; paired t test, **, P < 0.01; n = 7 sites), (C) τRise (control: 13 ± 4 ms; TTX: 9 ± 4 ms; paired t test, **, P < 0.01; n = 7 sites), and (D) τDecay (control: 145 ± 88 ms; TTX: 75 ± 48 ms; paired t test, *, P < 0.05; n = 7 sites). Black dots represent mean ± SEM.
© Copyright Policy - openaccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4664828&req=5

fig8: AutoR-mediated responses are amplified by activation of Nav channels. (A) Representative traces of average laser-evoked ASPs in control (black) and in TTX (gray; 400 nM). Summary plot of TTX effect on (B) ASP amplitude (control: 3.1 ± 1 mV; TTX: 1.9 ± 1 mV; paired t test, **, P < 0.01; n = 7 sites), (C) τRise (control: 13 ± 4 ms; TTX: 9 ± 4 ms; paired t test, **, P < 0.01; n = 7 sites), and (D) τDecay (control: 145 ± 88 ms; TTX: 75 ± 48 ms; paired t test, *, P < 0.05; n = 7 sites). Black dots represent mean ± SEM.
Mentions: Upon photolysis of DM-nitrophen, two net OH ions are formed per molecule of Ca2+ DM-nitrophen photolyzed. To buffer this pH change, 50 mM HEPES was used (see composition of IS above). Even with this high HEPES concentration, a pH change of ≈0.37 pH units is expected; in similar experimental conditions, this pH change had no effect on synaptic transmission (Trigo et al., 2012). The number of repetitions that can be performed when intracellularly photolyzing DM-nitrophen is limited. In this work, the maximum number of repetitions were 12 and 22 with high and low [Cl−]i solutions, respectively. This is not caused by direct photodamage with the 405-nm laser because it is not observed when photolyzing other caged compounds in the extracellular milieu, like glutamate or GABA, with the same method (Trigo et al., 2009b; this work, Fig. 8); rather, it may be caused by the release of oxidizing subproducts (nitrosoacetophenone; Kaplan and Ellis-Davies, 1988), but the exact mechanisms remain to be explored.

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