PMID- 11837948
OWN - NLM
STAT- MEDLINE
DCOM- 20020723
LR  - 20170214
IS  - 0748-7304 (Print)
IS  - 0748-7304 (Linking)
VI  - 17
IP  - 1
DP  - 2002 Feb
TI  - The suprachiasmatic nucleus exhibits diurnal variations in spontaneous excitatory 
      postsynaptic activity.
PG  - 40-51
AB  - A most prominent feature of neurons in the suprachiasmatic nucleus (SCN) is the 
      circadian rhythm in spontaneous firing frequency. To disclose synaptic mechanisms 
      associated with the rhythmic activity, the spontaneous postsynaptic activity was 
      studied using whole-cell, patch clamp recordings in the ventral region of the SCN 
      in slice preparations from rats. The synaptic events were compared between two 
      time intervals corresponding to the highest and lowest electrical activity within 
      the SCN during subjective daytime and nighttime, respectively. The 
      gamma-aminobutyric acid (GABA)-mediated spontaneous inhibitory activity showed no 
      diurnal variations, but the excitatory activity was markedly higher in frequency, 
      without differences in amplitude, during the subjective day compared to the 
      subjective night. Spontaneous and evoked inhibitory synaptic events were blocked 
      by the GABA(A) receptor antagonist bicuculline. The 
      alpha-amino-hydroxy-5-methylisoxazole-4-propionic acid (AMPA/kainate) receptor 
      antagonist 6-cyano-7-nitroquinoxaline-2, 3-dione (CNQX) blocked most of the 
      excitatory activity. In addition, CNQX reduced the spontaneous inhibitory 
      activity. The N-methyl-D-aspartate antagonist D-2-amino-5-phosphonopentanoic acid 
      reduced the inhibitory activity to a lesser degree, and there was no significant 
      difference in amplitude or frequency of synaptic events in control and Mg2+-free 
      solutions, indicating that the AMPA receptor plays an important role in 
      regulating the inhibitory release of GABA within the SCN. Ipsi- and contralateral 
      stimulation of the SCN consistently evoked excitatory synaptic responses. 
      Inhibitory synaptic responses occurred in some neurons upon increasing stimulus 
      strength. In conclusion, this study shows that there is a substantial influence 
      from spontaneous glutamatergic synapses on the ventral part of the SCN and that 
      these exhibit daily variations in activity. Diurnal fluctuations in spontaneous 
      excitatory postsynaptic activity within this network may contribute to the 
      mechanisms for synchronization of rhythms between individual SCN neurons and may 
      underlie the daily variations in the spontaneous firing frequency of SCN neurons.
FAU - Lundkvist, Gabriella B
AU  - Lundkvist GB
AD  - Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden. 
      Russell.Hill@neuro.ki.se
FAU - Kristensson, Krister
AU  - Kristensson K
FAU - Hill, Russell H
AU  - Hill RH
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - J Biol Rhythms
JT  - Journal of biological rhythms
JID - 8700115
RN  - 0 (Excitatory Amino Acid Antagonists)
RN  - 0 (Receptors, AMPA)
RN  - 0 (Receptors, GABA-A)
RN  - 3KX376GY7L (Glutamic Acid)
RN  - 6OTE87SCCW (6-Cyano-7-nitroquinoxaline-2,3-dione)
SB  - IM
MH  - 6-Cyano-7-nitroquinoxaline-2,3-dione/pharmacology
MH  - Animals
MH  - Circadian Rhythm/*physiology
MH  - Electric Stimulation
MH  - Electrophysiology
MH  - Evoked Potentials/physiology
MH  - Excitatory Amino Acid Antagonists/pharmacology
MH  - Excitatory Postsynaptic Potentials/*physiology
MH  - Glutamic Acid/physiology
MH  - Male
MH  - Neurons/physiology
MH  - Patch-Clamp Techniques
MH  - Rats
MH  - Rats, Sprague-Dawley
MH  - Receptors, AMPA/drug effects/physiology
MH  - Receptors, GABA-A/drug effects/physiology
MH  - Suprachiasmatic Nucleus/*physiology
EDAT- 2002/02/12 10:00
MHDA- 2002/07/24 10:01
CRDT- 2002/02/12 10:00
PHST- 2002/02/12 10:00 [pubmed]
PHST- 2002/07/24 10:01 [medline]
PHST- 2002/02/12 10:00 [entrez]
AID - 10.1177/074873002129002320 [doi]
PST - ppublish
SO  - J Biol Rhythms. 2002 Feb;17(1):40-51. doi: 10.1177/074873002129002320.