Zinc modulation of bicuculline-sensitive and -insensitive GABA receptors in the developing rat hippocampus

Marco Martina, Jerzy W. Mozrzymas, Fabrizio Strata, Enrico Cherubini*

*Corresponding author for this work

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Intracellular recordings were used to study the effects of zinc on the bicuculline-sensitive and -insensitive responses evoked by GABA in CA3 rat hippocampal neurons in slices obtained from postnatal day (P) 0 to P8. In the absence of bicuculline, zinc inhibited GABA-induced responses in a concentration-dependent manner. This effect was developmentally regulated, being maximal (50%) between P0 and P5 and then declining to 30% after P5. In the presence of bicuculline, GABA-resistant responses were potentiated in 49% of cases, depressed in 38% and not affected in 13%. The period of maximum potentiation between P0 and P2 coincided with that of maximum expression of the bicuculline-resistant receptors. The effects of zinc were also studied using the whole-cell and outside-out configuration of the patch-clamp technique on bicuculline-sensitive and -insensitive GABA-induced currents elicited in isolated cells acutely dissociated from the same slices as those used for intracellular recordings. At a holding potential of -50 mV in symmetrical chloride solutions, GABA (50 and 100 μM) activated whole-cell inward currents which were reversibly blocked by zinc. The EC50 values for the blocking effect of zinc on currents evoked by 50 and 100 μM GABA were 6.6 nM and 5.8 μM respectively. In the presence of bicuculline (100 μM), zinc potentiated the residual responses to GABA; the response curve was bell-shaped with a peak at 1 μM. When the response to GABA was completely abolished by bicuculline, zinc (1 μM) was often able to restore it. In the presence of bicuculline, however, zinc was not able to restore the response to isoguvacine. In two excised outside-out patches, zinc (1 μM) increased the activity of opening of bicuculline-resistant GABA-evoked single channel currents (Np) from 1 to 1.87 and from 0.25 to 0.42 respectively, without changing single-channel conductance. These data suggest that down- or up-regulation of bicuculline-sensitive or -insensitive GABA receptors may be functionally important in regulating synaptic activity during development.

Original languageEnglish (US)
Pages (from-to)2168-2176
Number of pages9
JournalEuropean Journal of Neuroscience
Volume8
Issue number10
DOIs
StatePublished - Oct 29 1996

Fingerprint

GABA Receptors
Bicuculline
Zinc
Hippocampus
gamma-Aminobutyric Acid
Patch-Clamp Techniques
Chlorides
Up-Regulation
Down-Regulation
Neurons

Keywords

  • Development
  • GABA(A)
  • GABA(C)
  • Isoguvacine

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Martina, Marco ; Mozrzymas, Jerzy W. ; Strata, Fabrizio ; Cherubini, Enrico. / Zinc modulation of bicuculline-sensitive and -insensitive GABA receptors in the developing rat hippocampus. In: European Journal of Neuroscience. 1996 ; Vol. 8, No. 10. pp. 2168-2176.
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abstract = "Intracellular recordings were used to study the effects of zinc on the bicuculline-sensitive and -insensitive responses evoked by GABA in CA3 rat hippocampal neurons in slices obtained from postnatal day (P) 0 to P8. In the absence of bicuculline, zinc inhibited GABA-induced responses in a concentration-dependent manner. This effect was developmentally regulated, being maximal (50{\%}) between P0 and P5 and then declining to 30{\%} after P5. In the presence of bicuculline, GABA-resistant responses were potentiated in 49{\%} of cases, depressed in 38{\%} and not affected in 13{\%}. The period of maximum potentiation between P0 and P2 coincided with that of maximum expression of the bicuculline-resistant receptors. The effects of zinc were also studied using the whole-cell and outside-out configuration of the patch-clamp technique on bicuculline-sensitive and -insensitive GABA-induced currents elicited in isolated cells acutely dissociated from the same slices as those used for intracellular recordings. At a holding potential of -50 mV in symmetrical chloride solutions, GABA (50 and 100 μM) activated whole-cell inward currents which were reversibly blocked by zinc. The EC50 values for the blocking effect of zinc on currents evoked by 50 and 100 μM GABA were 6.6 nM and 5.8 μM respectively. In the presence of bicuculline (100 μM), zinc potentiated the residual responses to GABA; the response curve was bell-shaped with a peak at 1 μM. When the response to GABA was completely abolished by bicuculline, zinc (1 μM) was often able to restore it. In the presence of bicuculline, however, zinc was not able to restore the response to isoguvacine. In two excised outside-out patches, zinc (1 μM) increased the activity of opening of bicuculline-resistant GABA-evoked single channel currents (Np) from 1 to 1.87 and from 0.25 to 0.42 respectively, without changing single-channel conductance. These data suggest that down- or up-regulation of bicuculline-sensitive or -insensitive GABA receptors may be functionally important in regulating synaptic activity during development.",
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Zinc modulation of bicuculline-sensitive and -insensitive GABA receptors in the developing rat hippocampus. / Martina, Marco; Mozrzymas, Jerzy W.; Strata, Fabrizio; Cherubini, Enrico.

In: European Journal of Neuroscience, Vol. 8, No. 10, 29.10.1996, p. 2168-2176.

Research output: Contribution to journalArticle

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T1 - Zinc modulation of bicuculline-sensitive and -insensitive GABA receptors in the developing rat hippocampus

AU - Martina, Marco

AU - Mozrzymas, Jerzy W.

AU - Strata, Fabrizio

AU - Cherubini, Enrico

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N2 - Intracellular recordings were used to study the effects of zinc on the bicuculline-sensitive and -insensitive responses evoked by GABA in CA3 rat hippocampal neurons in slices obtained from postnatal day (P) 0 to P8. In the absence of bicuculline, zinc inhibited GABA-induced responses in a concentration-dependent manner. This effect was developmentally regulated, being maximal (50%) between P0 and P5 and then declining to 30% after P5. In the presence of bicuculline, GABA-resistant responses were potentiated in 49% of cases, depressed in 38% and not affected in 13%. The period of maximum potentiation between P0 and P2 coincided with that of maximum expression of the bicuculline-resistant receptors. The effects of zinc were also studied using the whole-cell and outside-out configuration of the patch-clamp technique on bicuculline-sensitive and -insensitive GABA-induced currents elicited in isolated cells acutely dissociated from the same slices as those used for intracellular recordings. At a holding potential of -50 mV in symmetrical chloride solutions, GABA (50 and 100 μM) activated whole-cell inward currents which were reversibly blocked by zinc. The EC50 values for the blocking effect of zinc on currents evoked by 50 and 100 μM GABA were 6.6 nM and 5.8 μM respectively. In the presence of bicuculline (100 μM), zinc potentiated the residual responses to GABA; the response curve was bell-shaped with a peak at 1 μM. When the response to GABA was completely abolished by bicuculline, zinc (1 μM) was often able to restore it. In the presence of bicuculline, however, zinc was not able to restore the response to isoguvacine. In two excised outside-out patches, zinc (1 μM) increased the activity of opening of bicuculline-resistant GABA-evoked single channel currents (Np) from 1 to 1.87 and from 0.25 to 0.42 respectively, without changing single-channel conductance. These data suggest that down- or up-regulation of bicuculline-sensitive or -insensitive GABA receptors may be functionally important in regulating synaptic activity during development.

AB - Intracellular recordings were used to study the effects of zinc on the bicuculline-sensitive and -insensitive responses evoked by GABA in CA3 rat hippocampal neurons in slices obtained from postnatal day (P) 0 to P8. In the absence of bicuculline, zinc inhibited GABA-induced responses in a concentration-dependent manner. This effect was developmentally regulated, being maximal (50%) between P0 and P5 and then declining to 30% after P5. In the presence of bicuculline, GABA-resistant responses were potentiated in 49% of cases, depressed in 38% and not affected in 13%. The period of maximum potentiation between P0 and P2 coincided with that of maximum expression of the bicuculline-resistant receptors. The effects of zinc were also studied using the whole-cell and outside-out configuration of the patch-clamp technique on bicuculline-sensitive and -insensitive GABA-induced currents elicited in isolated cells acutely dissociated from the same slices as those used for intracellular recordings. At a holding potential of -50 mV in symmetrical chloride solutions, GABA (50 and 100 μM) activated whole-cell inward currents which were reversibly blocked by zinc. The EC50 values for the blocking effect of zinc on currents evoked by 50 and 100 μM GABA were 6.6 nM and 5.8 μM respectively. In the presence of bicuculline (100 μM), zinc potentiated the residual responses to GABA; the response curve was bell-shaped with a peak at 1 μM. When the response to GABA was completely abolished by bicuculline, zinc (1 μM) was often able to restore it. In the presence of bicuculline, however, zinc was not able to restore the response to isoguvacine. In two excised outside-out patches, zinc (1 μM) increased the activity of opening of bicuculline-resistant GABA-evoked single channel currents (Np) from 1 to 1.87 and from 0.25 to 0.42 respectively, without changing single-channel conductance. These data suggest that down- or up-regulation of bicuculline-sensitive or -insensitive GABA receptors may be functionally important in regulating synaptic activity during development.

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