Sometimes you see them, sometimes you don't: IPSCs in the rat superficial superior colliculus

Michelle Diane Edwards, Bettina Platt

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Superficial superior colliculus (SSC) neurones were voltage-clamped and the current-voltage relationship of synaptically evoked currents analyzed in vitro. A strong interplay between. excitatory postsynaptic currents (EPSCs) and inhibitory postsynaptic currents (IPSCs) was identified. Glutamate receptor antagonists not only fully blocked EPSCs but IPSCs were also frequently reduced by the specific D,L,alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist (by 66.9%), indicative of glutamate-driven inhibitory projections. The GABA(A) receptor antagonist bicuculline enhanced EPSCs and either abolished or reduced (by 79.3%) IPSCs. The GABA(C) receptor antagonist 1,2,5,6-tetrahydro-(pyridin-4-yl)methylphosphinic acid decreased IPSCs in 80% of cells tested (by 24.1%), but had no effect on EPSCs. Varying the recording conditions influenced postsynaptic currents. At a holding potential of -60 mV, IPSCs were generally produced with intracellular chloride concentrations of both 5 and 10 mM (total n=24/30). However, with perforated-patch recordings using gramicidin, IPSCs were less frequently encountered (n=5121), suggesting a higher intracellular chloride concentration in a large proportion of SSC neurones. Further assessment of experimental conditions revealed that two frequently used sodium channel blockers, QX-314 (bromide salt, intracellular) or tetrodotoxin (extracellular), shifted the IPSC reversal potential towards more positive values. Hence, IPSCs were not encountered at -60 mV in their presence. The level of stimulation intensity (minimal or maximal) did not influence IPSC production in these conditions. Thus, the current study describes the pharmacological properties of EPSCs in the SSC and highlights the impact of experimental conditions on synaptic transmission, which requires consideration for past and present data reported in this preparation.

Original languageEnglish
Pages (from-to)331-339
Number of pages8
JournalExperimental Brain Research
Volume149
Issue number3
DOIs
Publication statusPublished - 2003

Keywords

  • chloride equilibrium
  • GABA
  • gramacidin
  • QX-314
  • synaptic transmission
  • LOCAL-ANESTHETIC QX-314
  • LONG-TERM POTENTIATION
  • K-CL COTRANSPORTER
  • DIFFERENTIAL EXPRESSION
  • PYRAMIDAL NEURONS
  • SYNAPTIC CURRENTS
  • GABA(C) RECEPTORS
  • SODIUM CURRENTS
  • INHIBITION
  • LAYERS

Cite this

Sometimes you see them, sometimes you don't: IPSCs in the rat superficial superior colliculus. / Edwards, Michelle Diane; Platt, Bettina.

In: Experimental Brain Research, Vol. 149, No. 3, 2003, p. 331-339.

Research output: Contribution to journalArticle

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abstract = "Superficial superior colliculus (SSC) neurones were voltage-clamped and the current-voltage relationship of synaptically evoked currents analyzed in vitro. A strong interplay between. excitatory postsynaptic currents (EPSCs) and inhibitory postsynaptic currents (IPSCs) was identified. Glutamate receptor antagonists not only fully blocked EPSCs but IPSCs were also frequently reduced by the specific D,L,alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist (by 66.9{\%}), indicative of glutamate-driven inhibitory projections. The GABA(A) receptor antagonist bicuculline enhanced EPSCs and either abolished or reduced (by 79.3{\%}) IPSCs. The GABA(C) receptor antagonist 1,2,5,6-tetrahydro-(pyridin-4-yl)methylphosphinic acid decreased IPSCs in 80{\%} of cells tested (by 24.1{\%}), but had no effect on EPSCs. Varying the recording conditions influenced postsynaptic currents. At a holding potential of -60 mV, IPSCs were generally produced with intracellular chloride concentrations of both 5 and 10 mM (total n=24/30). However, with perforated-patch recordings using gramicidin, IPSCs were less frequently encountered (n=5121), suggesting a higher intracellular chloride concentration in a large proportion of SSC neurones. Further assessment of experimental conditions revealed that two frequently used sodium channel blockers, QX-314 (bromide salt, intracellular) or tetrodotoxin (extracellular), shifted the IPSC reversal potential towards more positive values. Hence, IPSCs were not encountered at -60 mV in their presence. The level of stimulation intensity (minimal or maximal) did not influence IPSC production in these conditions. Thus, the current study describes the pharmacological properties of EPSCs in the SSC and highlights the impact of experimental conditions on synaptic transmission, which requires consideration for past and present data reported in this preparation.",
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N2 - Superficial superior colliculus (SSC) neurones were voltage-clamped and the current-voltage relationship of synaptically evoked currents analyzed in vitro. A strong interplay between. excitatory postsynaptic currents (EPSCs) and inhibitory postsynaptic currents (IPSCs) was identified. Glutamate receptor antagonists not only fully blocked EPSCs but IPSCs were also frequently reduced by the specific D,L,alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist (by 66.9%), indicative of glutamate-driven inhibitory projections. The GABA(A) receptor antagonist bicuculline enhanced EPSCs and either abolished or reduced (by 79.3%) IPSCs. The GABA(C) receptor antagonist 1,2,5,6-tetrahydro-(pyridin-4-yl)methylphosphinic acid decreased IPSCs in 80% of cells tested (by 24.1%), but had no effect on EPSCs. Varying the recording conditions influenced postsynaptic currents. At a holding potential of -60 mV, IPSCs were generally produced with intracellular chloride concentrations of both 5 and 10 mM (total n=24/30). However, with perforated-patch recordings using gramicidin, IPSCs were less frequently encountered (n=5121), suggesting a higher intracellular chloride concentration in a large proportion of SSC neurones. Further assessment of experimental conditions revealed that two frequently used sodium channel blockers, QX-314 (bromide salt, intracellular) or tetrodotoxin (extracellular), shifted the IPSC reversal potential towards more positive values. Hence, IPSCs were not encountered at -60 mV in their presence. The level of stimulation intensity (minimal or maximal) did not influence IPSC production in these conditions. Thus, the current study describes the pharmacological properties of EPSCs in the SSC and highlights the impact of experimental conditions on synaptic transmission, which requires consideration for past and present data reported in this preparation.

AB - Superficial superior colliculus (SSC) neurones were voltage-clamped and the current-voltage relationship of synaptically evoked currents analyzed in vitro. A strong interplay between. excitatory postsynaptic currents (EPSCs) and inhibitory postsynaptic currents (IPSCs) was identified. Glutamate receptor antagonists not only fully blocked EPSCs but IPSCs were also frequently reduced by the specific D,L,alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist (by 66.9%), indicative of glutamate-driven inhibitory projections. The GABA(A) receptor antagonist bicuculline enhanced EPSCs and either abolished or reduced (by 79.3%) IPSCs. The GABA(C) receptor antagonist 1,2,5,6-tetrahydro-(pyridin-4-yl)methylphosphinic acid decreased IPSCs in 80% of cells tested (by 24.1%), but had no effect on EPSCs. Varying the recording conditions influenced postsynaptic currents. At a holding potential of -60 mV, IPSCs were generally produced with intracellular chloride concentrations of both 5 and 10 mM (total n=24/30). However, with perforated-patch recordings using gramicidin, IPSCs were less frequently encountered (n=5121), suggesting a higher intracellular chloride concentration in a large proportion of SSC neurones. Further assessment of experimental conditions revealed that two frequently used sodium channel blockers, QX-314 (bromide salt, intracellular) or tetrodotoxin (extracellular), shifted the IPSC reversal potential towards more positive values. Hence, IPSCs were not encountered at -60 mV in their presence. The level of stimulation intensity (minimal or maximal) did not influence IPSC production in these conditions. Thus, the current study describes the pharmacological properties of EPSCs in the SSC and highlights the impact of experimental conditions on synaptic transmission, which requires consideration for past and present data reported in this preparation.

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KW - GABA

KW - gramacidin

KW - QX-314

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KW - LONG-TERM POTENTIATION

KW - K-CL COTRANSPORTER

KW - DIFFERENTIAL EXPRESSION

KW - PYRAMIDAL NEURONS

KW - SYNAPTIC CURRENTS

KW - GABA(C) RECEPTORS

KW - SODIUM CURRENTS

KW - INHIBITION

KW - LAYERS

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DO - 10.1007/s00221-002-1368-2

M3 - Article

VL - 149

SP - 331

EP - 339

JO - Experimental Brain Research

JF - Experimental Brain Research

SN - 0014-4819

IS - 3

ER -