Search our Database of Scientific Publications and Authors

I’m looking for a

    Details and Download Full Text PDF:
    The suprachiasmatic nucleus exhibits diurnal variations in spontaneous excitatory postsynaptic activity.

    J Biol Rhythms 2002 Feb;17(1):40-51
    Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
    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.
    PDF Download - Full Text Link
    ( Please be advised that this article is hosted on an external website not affiliated with
    Source Status ListingPossible

    Similar Publications

    Excitatory mechanisms in the suprachiasmatic nucleus: the role of AMPA/KA glutamate receptors.
    J Neurophysiol 2002 Aug;88(2):817-28
    Mental Retardation Research Center, Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles 90024-1759, USA.
    A variety of evidence suggests that the effects of light on the mammalian circadian system are mediated by direct retinal ganglion cell projection to the suprachiasmatic nucleus (SCN). This synaptic connection is glutamatergic and the release of glutamate is detected by both N-methyl-D-asparate (NMDA) and amino-methyl proprionic acid/kainate (AMPA/KA) iontotropic glutamate receptors (GluRs). It is well established that NMDA GluRs play a critical role in mediating the effects of light on the circadian system; however, the role of AMPA/KA GluRs has received less attention. Read More
    Nociceptin/orphanin FQ (N/OFQ) inhibits excitatory and inhibitory synaptic signaling in the suprachiasmatic nucleus (SCN).
    Neuroscience 2005 ;132(4):955-65
    Center for Research on Occupational and Environmental Toxicology, Oregon Health and Science University, Portland, 97239-3098, USA.
    Environmental synchronization of the endogenous mammalian circadian rhythm involves glutamatergic and GABAergic neurotransmission within the hypothalamic suprachiasmatic nucleus (SCN). The neuropeptide nociceptin/orphanin FQ (N/OFQ) inhibits light-induced phase shifts, evokes K(+)-currents and reduces the intracellular Ca(2+) concentration in SCN neurons. Since these effects are consistent with a modulatory role for N/OFQ on synaptic transmission in the SCN, we examined the effects of N/OFQ on evoked and spontaneous excitatory and inhibitory currents in the SCN. Read More
    Presynaptic inhibition by baclofen of retinohypothalamic excitatory synaptic transmission in rat suprachiasmatic nucleus.
    Neuroscience 1995 Feb;64(3):813-9
    Vollum Institute for Advanced Biomedical Research, Oregon Health Sciences University, Portland 97201-3098, USA.
    Optic nerve stimulation evoked monosynaptic excitatory postsynaptic currents in suprachiasmatic nucleus neurons maintained in vitro. These currents were completely blocked by a combination of glutamate receptor antagonists, 6-cyano-7-nitroquinoxaline-2,3-dione and 4-aminophosphonovaleric acid. Stimulation of the ipsilateral or contralateral suprachiasmatic nucleus produced a biphasic response consisting of an excitatory postsynaptic current followed by an bicuculline-sensitive inhibitory postsynaptic current. Read More
    Mechanisms underlying the enhancement of excitatory synaptic transmission in basolateral amygdala neurons of the kindling rat.
    J Neurophysiol 1998 Aug;80(2):638-46
    Department of Physiology, Kurume University School of Medicine, Kurume 830, Japan.
    To elucidate the mechanism underlying epileptiform discharges in kindled rats, synaptic responses in kindled basolateral amygdala neurons in vitro were compared with those from control rats by using intracellular and whole cell patch-clamp recordings. In kindled neurons, electrical stimulation of the stria terminalis induced epileptiform discharges. The resting potential, apparent input resistance, current-voltage relationship of the membrane, and the threshold, amplitude, and duration of action potentials in kindled neurons were not different from those in control neurons. Read More