TY - JOUR
T1 - Membrane properties and synaptic inputs of suprachiasmatic nucleus neurons in rat brain slices
AU - Jiang, Zhi Gen
AU - Yang, Yu Qin
AU - Liu, Zhao Ping
AU - Allen, Charles N.
N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 1997/2/15
Y1 - 1997/2/15
N2 - 1. Whole-cell. recordings were made from 390 neurons of the suprachiasmatic nucleus (SCN) in horizontal brain slices during different portions of the circadian day. The locomotor activity of the rats was measured prior to the preparation of brain slices to insure that each rat was entrained to a 12 h-12 h light-dark cycle. The mean input conductance was 42% higher (1.58 nS) in neurons recorded near the subjective dawn than those (1.11 nS) recorded near the subjective dusk. The current required to hold the neurons at -60 mV also showed a circadian variation with a peak in the middle of the subjective day and a nadir in the middle of the subjective night. Analysis of the variations in the input conductance and the holding current at -60 mV suggested that at least two ion conductances are involved in the pacemaking of the circadian rhythms. 3. Voltage-clamped SCN neurons often had both outward and inward spontaneous postsynaptic currents. The outward currents were blocked by bicuculline but not by strychnine, and were identified as IPSCs mediated by GABA(A) receptors. The inward currents were blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and were identified as EPXCs mediated by glutamate. Most spontaneous synaptic currents were miniature currents but action potential-dependent large events were seen more often in IPSCs than in EPSCs. 4. Stimulation of the optic nerve or chiasm usually evoked a monosynaptic EPSC which was mediated by both NMDA and non-NMDA receptors. In 13% of cells, optic nerve stimulation evoked an outward current or an inward current followed by an outward current; all the evoked currents were blocked by 4-aminophosphonovaleric acid (APV)and CNQX whereas the outward current only was blocked by bicuculline, suggesting involvement of an inhibitory interneuron. 5. SCN neurons sum the excitatory inputs from both optic nerves; on average each SCN cell receives innervation from at least 4.8 retinohypothalamic tract (RHT) axons. 6. Focal stimulation in the vicinity of the recorded neuron revealed that nearly all SCN neurons receive local or extranuclear GABAergic inputs operating via GABA(A) receptors. The EPSCs activated by such stimulation were not significantly different in amplitude and pharmacological properties from those induced by RHT stimulation. One hundred and one neurons were labelled with neurobiotin during whole-cell, recording. Based on the dendritic structures, four types of SCN neurons (monopolar, radial, simple bipolar and curly bipolar) were identified. The curly bipolar cells had a higher membrane conductance, holding current and hyperpolarization-activated current (I(h)) amplitude than the other neuronal types. Radial neurons did not respond to optic nerve stimulation, which activated EPSCs in the other cell types.
AB - 1. Whole-cell. recordings were made from 390 neurons of the suprachiasmatic nucleus (SCN) in horizontal brain slices during different portions of the circadian day. The locomotor activity of the rats was measured prior to the preparation of brain slices to insure that each rat was entrained to a 12 h-12 h light-dark cycle. The mean input conductance was 42% higher (1.58 nS) in neurons recorded near the subjective dawn than those (1.11 nS) recorded near the subjective dusk. The current required to hold the neurons at -60 mV also showed a circadian variation with a peak in the middle of the subjective day and a nadir in the middle of the subjective night. Analysis of the variations in the input conductance and the holding current at -60 mV suggested that at least two ion conductances are involved in the pacemaking of the circadian rhythms. 3. Voltage-clamped SCN neurons often had both outward and inward spontaneous postsynaptic currents. The outward currents were blocked by bicuculline but not by strychnine, and were identified as IPSCs mediated by GABA(A) receptors. The inward currents were blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and were identified as EPXCs mediated by glutamate. Most spontaneous synaptic currents were miniature currents but action potential-dependent large events were seen more often in IPSCs than in EPSCs. 4. Stimulation of the optic nerve or chiasm usually evoked a monosynaptic EPSC which was mediated by both NMDA and non-NMDA receptors. In 13% of cells, optic nerve stimulation evoked an outward current or an inward current followed by an outward current; all the evoked currents were blocked by 4-aminophosphonovaleric acid (APV)and CNQX whereas the outward current only was blocked by bicuculline, suggesting involvement of an inhibitory interneuron. 5. SCN neurons sum the excitatory inputs from both optic nerves; on average each SCN cell receives innervation from at least 4.8 retinohypothalamic tract (RHT) axons. 6. Focal stimulation in the vicinity of the recorded neuron revealed that nearly all SCN neurons receive local or extranuclear GABAergic inputs operating via GABA(A) receptors. The EPSCs activated by such stimulation were not significantly different in amplitude and pharmacological properties from those induced by RHT stimulation. One hundred and one neurons were labelled with neurobiotin during whole-cell, recording. Based on the dendritic structures, four types of SCN neurons (monopolar, radial, simple bipolar and curly bipolar) were identified. The curly bipolar cells had a higher membrane conductance, holding current and hyperpolarization-activated current (I(h)) amplitude than the other neuronal types. Radial neurons did not respond to optic nerve stimulation, which activated EPSCs in the other cell types.
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U2 - 10.1113/jphysiol.1997.sp021917
DO - 10.1113/jphysiol.1997.sp021917
M3 - Article
C2 - 9061646
AN - SCOPUS:0031051454
SN - 0022-3751
VL - 499
SP - 141
EP - 159
JO - Journal of Physiology
JF - Journal of Physiology
IS - 1
ER -