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Involvement of Potassium and Cation Channels in Hippocampal Abnormalities of Embryonic Ts65Dn and Tc1 Trisomic Mice.

Stern S, Segal M, Moses E - EBioMedicine (2015)

Bottom Line: We found a decrease of ~ 30% in both fast (A-type) and slow (delayed rectifier) outward potassium currents.Their network bursts were smaller and slower than diploids, displaying a 40% reduction in Δf / f0 of the calcium signals, and a 30% reduction in propagation velocity.Additionally, Ts65Dn and Tc1 neurons exhibited changes in the action potential shape compared to diploid neurons, with an increase in the amplitude of the action potential, a lower threshold for spiking, and a sharp decrease of about 65% in the after-hyperpolarization amplitude.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics of Complex Systems, Weizmann Institute of Science, P.O. Box 26, Rehovot 76100 Israel.

ABSTRACT
Down syndrome (DS) mouse models exhibit cognitive deficits, and are used for studying the neuronal basis of DS pathology. To understand the differences in the physiology of DS model neurons, we used dissociated neuronal cultures from the hippocampi of Ts65Dn and Tc1 DS mice. Imaging of [Ca(2+)]i and whole cell patch clamp recordings were used to analyze network activity and single neuron properties, respectively. We found a decrease of ~ 30% in both fast (A-type) and slow (delayed rectifier) outward potassium currents. Depolarization of Ts65Dn and Tc1 cells produced fewer spikes than diploid cells. Their network bursts were smaller and slower than diploids, displaying a 40% reduction in Δf / f0 of the calcium signals, and a 30% reduction in propagation velocity. Additionally, Ts65Dn and Tc1 neurons exhibited changes in the action potential shape compared to diploid neurons, with an increase in the amplitude of the action potential, a lower threshold for spiking, and a sharp decrease of about 65% in the after-hyperpolarization amplitude. Numerical simulations reproduced the DS measured phenotype by variations in the conductance of the delayed rectifier and A-type, but necessitated also changes in inward rectifying and M-type potassium channels and in the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. We therefore conducted whole cell patch clamp measurements of M-type potassium currents, which showed a ~ 90% decrease in Ts65Dn neurons, while HCN measurements displayed an increase of ~ 65% in Ts65Dn cells. Quantitative real-time PCR analysis indicates overexpression of 40% of KCNJ15, an inward rectifying potassium channel, contributing to the increased inhibition. We thus find that changes in several types of potassium channels dominate the observed DS model phenotype.

No MeSH data available.


Related in: MedlinePlus

Analysis of spontaneous network bursts and miniature EPSCs measured with whole cell patch clamp. a, Example of currents recorded during network burst activity for a diploid network (DIV > 12). b, A zoom in on the example recording of the diploid network shown in a. c, Example of currents recorded as in a, for a Ts65Dn network (DIV > 12). d, A zoom in on the example recording of the Ts65Dn network shown in c. e, Mean burst duration for cultures aged 10–11 DIV (diploid N = 11 cells, Ts65Dn N = 9 cells). f, Mean burst duration as in e, but for cultures with ages larger than 12 DIV, (diploid N = 11 cells, Ts65Dn N = 15 cells), p = 0.009. g, Total mean bursting time out of total recording time for cultures of ages 10–11 DIV (diploid N = 11 cells, Ts65Dn N = 9 cells). h, Total bursting time out of total recording time for cultures with ages larger than 12 DIV (diploid N = 11 cells, Ts65Dn N = 15 cells), p = 0.001. i, Mean burst duration for cultures with ages larger than 12 DIV (diploid N = 20 cells, Tc1 N = 21 cells). j, Total bursting time out of total recording time for cultures with ages larger than 12 DIV (diploid N = 20 cells, Tc1 N = 21 cells), p = 0.17. k, Example recording of mEPSCs recorded in the presence of TTX. Note the change in the scale of the y-axis from a and c. l, Mean recorded amplitude of mEPSCs (diploid N = 24 cells, Tc1 N = 29 cells). m, Mean mEPSCs frequency (diploid N = 24 cells, Tc1 N = 29 cells). For panels e–j and l–m results are given as mean ± SEM. * indicates p-value < 0.05, ** is p < 0.01, and *** indicates p < 0.001.
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f0015: Analysis of spontaneous network bursts and miniature EPSCs measured with whole cell patch clamp. a, Example of currents recorded during network burst activity for a diploid network (DIV > 12). b, A zoom in on the example recording of the diploid network shown in a. c, Example of currents recorded as in a, for a Ts65Dn network (DIV > 12). d, A zoom in on the example recording of the Ts65Dn network shown in c. e, Mean burst duration for cultures aged 10–11 DIV (diploid N = 11 cells, Ts65Dn N = 9 cells). f, Mean burst duration as in e, but for cultures with ages larger than 12 DIV, (diploid N = 11 cells, Ts65Dn N = 15 cells), p = 0.009. g, Total mean bursting time out of total recording time for cultures of ages 10–11 DIV (diploid N = 11 cells, Ts65Dn N = 9 cells). h, Total bursting time out of total recording time for cultures with ages larger than 12 DIV (diploid N = 11 cells, Ts65Dn N = 15 cells), p = 0.001. i, Mean burst duration for cultures with ages larger than 12 DIV (diploid N = 20 cells, Tc1 N = 21 cells). j, Total bursting time out of total recording time for cultures with ages larger than 12 DIV (diploid N = 20 cells, Tc1 N = 21 cells), p = 0.17. k, Example recording of mEPSCs recorded in the presence of TTX. Note the change in the scale of the y-axis from a and c. l, Mean recorded amplitude of mEPSCs (diploid N = 24 cells, Tc1 N = 29 cells). m, Mean mEPSCs frequency (diploid N = 24 cells, Tc1 N = 29 cells). For panels e–j and l–m results are given as mean ± SEM. * indicates p-value < 0.05, ** is p < 0.01, and *** indicates p < 0.001.

Mentions: Network activity was measured in individual neurons clamped at − 60 mV in cultures aged 10 to 15 DIV (Fig. 3). Fig. 3a and c shows examples of an 80 s recording interval of network activity from diploid and Ts65Dn cultures respectively, with a zoom-in on the first 8 s of recording given in Fig. 3b and d respectively. Fig. 3e and f shows the mean burst duration at different days of measurement, while Fig. 3g and h shows for the same days the amount of time that the culture spent bursting (with respect to the total recording time). For young cultures (10–11 DIV), the network activity was similar in Ts65Dn (N = 9 cells) and in diploid cultures (N = 11 cells) (Fig. 3e and g), but for cultures of age > 12 DIV, the diploid cultures had more and longer bursts than Ts65Dn cultures (Fig. 3f and h). Fig. 3f shows that after 12 DIV the mean burst duration for the diploid cultures was 3.03 ± 0.56 s (N = 11 cells), versus 1.34 ± 0.16 s for the Ts65Dn (N = 15 cells, p = 0.009). Fig. 3h shows that after 12 DIV diploid networks were more active: they spent 38.3 ± 5.5% (N = 11 cells) of the time bursting while Ts65Dn neurons spent only 9.9 ± 1.7% (N = 15 cells) of the time in bursts (p < 0.001).


Involvement of Potassium and Cation Channels in Hippocampal Abnormalities of Embryonic Ts65Dn and Tc1 Trisomic Mice.

Stern S, Segal M, Moses E - EBioMedicine (2015)

Analysis of spontaneous network bursts and miniature EPSCs measured with whole cell patch clamp. a, Example of currents recorded during network burst activity for a diploid network (DIV > 12). b, A zoom in on the example recording of the diploid network shown in a. c, Example of currents recorded as in a, for a Ts65Dn network (DIV > 12). d, A zoom in on the example recording of the Ts65Dn network shown in c. e, Mean burst duration for cultures aged 10–11 DIV (diploid N = 11 cells, Ts65Dn N = 9 cells). f, Mean burst duration as in e, but for cultures with ages larger than 12 DIV, (diploid N = 11 cells, Ts65Dn N = 15 cells), p = 0.009. g, Total mean bursting time out of total recording time for cultures of ages 10–11 DIV (diploid N = 11 cells, Ts65Dn N = 9 cells). h, Total bursting time out of total recording time for cultures with ages larger than 12 DIV (diploid N = 11 cells, Ts65Dn N = 15 cells), p = 0.001. i, Mean burst duration for cultures with ages larger than 12 DIV (diploid N = 20 cells, Tc1 N = 21 cells). j, Total bursting time out of total recording time for cultures with ages larger than 12 DIV (diploid N = 20 cells, Tc1 N = 21 cells), p = 0.17. k, Example recording of mEPSCs recorded in the presence of TTX. Note the change in the scale of the y-axis from a and c. l, Mean recorded amplitude of mEPSCs (diploid N = 24 cells, Tc1 N = 29 cells). m, Mean mEPSCs frequency (diploid N = 24 cells, Tc1 N = 29 cells). For panels e–j and l–m results are given as mean ± SEM. * indicates p-value < 0.05, ** is p < 0.01, and *** indicates p < 0.001.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588457&req=5

f0015: Analysis of spontaneous network bursts and miniature EPSCs measured with whole cell patch clamp. a, Example of currents recorded during network burst activity for a diploid network (DIV > 12). b, A zoom in on the example recording of the diploid network shown in a. c, Example of currents recorded as in a, for a Ts65Dn network (DIV > 12). d, A zoom in on the example recording of the Ts65Dn network shown in c. e, Mean burst duration for cultures aged 10–11 DIV (diploid N = 11 cells, Ts65Dn N = 9 cells). f, Mean burst duration as in e, but for cultures with ages larger than 12 DIV, (diploid N = 11 cells, Ts65Dn N = 15 cells), p = 0.009. g, Total mean bursting time out of total recording time for cultures of ages 10–11 DIV (diploid N = 11 cells, Ts65Dn N = 9 cells). h, Total bursting time out of total recording time for cultures with ages larger than 12 DIV (diploid N = 11 cells, Ts65Dn N = 15 cells), p = 0.001. i, Mean burst duration for cultures with ages larger than 12 DIV (diploid N = 20 cells, Tc1 N = 21 cells). j, Total bursting time out of total recording time for cultures with ages larger than 12 DIV (diploid N = 20 cells, Tc1 N = 21 cells), p = 0.17. k, Example recording of mEPSCs recorded in the presence of TTX. Note the change in the scale of the y-axis from a and c. l, Mean recorded amplitude of mEPSCs (diploid N = 24 cells, Tc1 N = 29 cells). m, Mean mEPSCs frequency (diploid N = 24 cells, Tc1 N = 29 cells). For panels e–j and l–m results are given as mean ± SEM. * indicates p-value < 0.05, ** is p < 0.01, and *** indicates p < 0.001.
Mentions: Network activity was measured in individual neurons clamped at − 60 mV in cultures aged 10 to 15 DIV (Fig. 3). Fig. 3a and c shows examples of an 80 s recording interval of network activity from diploid and Ts65Dn cultures respectively, with a zoom-in on the first 8 s of recording given in Fig. 3b and d respectively. Fig. 3e and f shows the mean burst duration at different days of measurement, while Fig. 3g and h shows for the same days the amount of time that the culture spent bursting (with respect to the total recording time). For young cultures (10–11 DIV), the network activity was similar in Ts65Dn (N = 9 cells) and in diploid cultures (N = 11 cells) (Fig. 3e and g), but for cultures of age > 12 DIV, the diploid cultures had more and longer bursts than Ts65Dn cultures (Fig. 3f and h). Fig. 3f shows that after 12 DIV the mean burst duration for the diploid cultures was 3.03 ± 0.56 s (N = 11 cells), versus 1.34 ± 0.16 s for the Ts65Dn (N = 15 cells, p = 0.009). Fig. 3h shows that after 12 DIV diploid networks were more active: they spent 38.3 ± 5.5% (N = 11 cells) of the time bursting while Ts65Dn neurons spent only 9.9 ± 1.7% (N = 15 cells) of the time in bursts (p < 0.001).

Bottom Line: We found a decrease of ~ 30% in both fast (A-type) and slow (delayed rectifier) outward potassium currents.Their network bursts were smaller and slower than diploids, displaying a 40% reduction in Δf / f0 of the calcium signals, and a 30% reduction in propagation velocity.Additionally, Ts65Dn and Tc1 neurons exhibited changes in the action potential shape compared to diploid neurons, with an increase in the amplitude of the action potential, a lower threshold for spiking, and a sharp decrease of about 65% in the after-hyperpolarization amplitude.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics of Complex Systems, Weizmann Institute of Science, P.O. Box 26, Rehovot 76100 Israel.

ABSTRACT
Down syndrome (DS) mouse models exhibit cognitive deficits, and are used for studying the neuronal basis of DS pathology. To understand the differences in the physiology of DS model neurons, we used dissociated neuronal cultures from the hippocampi of Ts65Dn and Tc1 DS mice. Imaging of [Ca(2+)]i and whole cell patch clamp recordings were used to analyze network activity and single neuron properties, respectively. We found a decrease of ~ 30% in both fast (A-type) and slow (delayed rectifier) outward potassium currents. Depolarization of Ts65Dn and Tc1 cells produced fewer spikes than diploid cells. Their network bursts were smaller and slower than diploids, displaying a 40% reduction in Δf / f0 of the calcium signals, and a 30% reduction in propagation velocity. Additionally, Ts65Dn and Tc1 neurons exhibited changes in the action potential shape compared to diploid neurons, with an increase in the amplitude of the action potential, a lower threshold for spiking, and a sharp decrease of about 65% in the after-hyperpolarization amplitude. Numerical simulations reproduced the DS measured phenotype by variations in the conductance of the delayed rectifier and A-type, but necessitated also changes in inward rectifying and M-type potassium channels and in the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. We therefore conducted whole cell patch clamp measurements of M-type potassium currents, which showed a ~ 90% decrease in Ts65Dn neurons, while HCN measurements displayed an increase of ~ 65% in Ts65Dn cells. Quantitative real-time PCR analysis indicates overexpression of 40% of KCNJ15, an inward rectifying potassium channel, contributing to the increased inhibition. We thus find that changes in several types of potassium channels dominate the observed DS model phenotype.

No MeSH data available.


Related in: MedlinePlus