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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(More)
Hyperexcited states, including depolarization block and depolarized low amplitude membrane oscillations (DLAMOs), have been observed in neurons of the suprachiasmatic nuclei (SCN), the site of the central mammalian circadian (~24-hour) clock. The causes and consequences of this hyperexcitation have not yet been determined. Here, we explore how individual(More)
The hypothalamic suprachiasmatic nucleus, the primary circadian pacemaker in mammals, and the retinohypothalamic tract, the retinal afferent fibres to the suprachiasmatic nucleus, both mature during early postnatal life. The establishment of circadian rhythms is thought to depend on input from the retina, but the mechanism remains unknown. Here we examined(More)
Intercellular communication between gamma-aminobutyric acid (GABA)ergic suprachiasmatic nucleus (SCN) neurons facilitates light-induced phase changes and synchronization of individual neural oscillators within the SCN network. We used ratiometric Ca(2+) imaging techniques to record changes in the intracellular calcium concentration ([Ca(2+)](i)) to study(More)
Acute isolation of hippocampal CA3 pyramidal cells using trypsin produces neurons which respond to kainate and quisqualate but not N-methyl-D-aspartate (NMDA). Incubation of 6- to 12-day-old cultured hippocampal neurons or slices of pyriform cortex with trypsin irreversibly removes the NMDA responses normally present without significant effect on responses(More)
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. 2. The mean input conductance was(More)
The effects of melatonin on circadian pacemaker activity in the central nervous system may be the result of melatonin receptor activation of G-protein coupled potassium channels which inhibit the action potential firing of neurons. Xenopus laevis and human1a melatonin receptors stimulated heteromeric G-protein activated inwardly rectifying potassium(More)
Intracellular free Ca(2+) regulates diverse cellular processes, including membrane potential, neurotransmitter release, and gene expression. To examine the cellular mechanisms underlying the generation of circadian rhythms, nucleus-targeted and untargeted cDNAs encoding a Ca(2+)-sensitive fluorescent protein (cameleon) were transfected into organotypic(More)
A small number (<2%) of mammalian retinal ganglion cells express the photopigment melanopsin and are intrinsically photosensitive (ipRGCs). Light depolarizes ipRGCs and increases intracellular calcium levels ([Ca2+]i) but the signaling cascades underlying these responses have yet to be elucidated. To facilitate physiological studies on these rare(More)
The effects of trimethyltin (TMT) on neurotransmitters, morphological changes and physiological activity of the hippocampus were studied. A single injection of TMT (8 mg/kg) decreased the high affinity uptake of glutamate (HA-Glu), which is a marker for glutamergic nerve terminals, after 7 days. The maximal reduction of HA-Glu was 42% and was obtained on(More)