title: Spontaneous and stimulated firing in cultured rat suprachiasmatic neurons.
abstract: Neurons from the suprachiasmatic nucleus (SCN) of the hypothalamus, the site of a circadian pacemaker in mammals, were isolated from embryonic rat. After mechanical dissociation neurons were brought into culture for 1-2 weeks, using a chemically defined medium. Recordings were made from 74 bipolar neurons using two different configurations of the patch-clamp technique. During cell attached patch recordings, 45% of neurons fired spontaneously. The mean firing rate was 0.7 +/- 0.6 Hz and the firing pattern was irregular. In whole cell recordings 73% of the investigated neurons showed spontaneous activity with an irregular firing pattern. The mean spontaneous firing rate with an intracellular Cl- concentration of 145 mM was 1.0 +/- 0.6 Hz. The resting membrane potential of the bipolar neurons was estimated to be -62 +/- 24 mV. An intracellular Cl- concentration of 145 mM depolarised the membrane potential. It also increased the probability of spontaneous firing. A depolarising current stimulus produced an action potential with a threshold voltage of -46 +/- 9 mV. Suprathreshold stimuli resulted in repetitive firing with a mean frequency of 12 +/- 4 Hz. The minimum interspike interval was 52 +/- 14 ms. All action potentials either occurring spontaneously or elicited by current stimuli were abolished by the Na(+)-channel blocker TTX. These results indicate that our cultured neurons have some electrophysiological properties in common with SCN neurons in brain slices and in vivo.
authors.affiliation: Department of Physiology, Leiden University, The Netherlands.
authors.forename: I B
authors.initials: IB
authors.lastname: Walsh
authors.forename: R J
authors.initials: RJ
authors.lastname: van den Berg
authors.forename: E
authors.initials: E
authors.lastname: Marani
authors.forename: W J
authors.initials: WJ
authors.lastname: Rietveld
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D004594:Electrophysiology; D005260:Female; D007473:Ion Channels / Q000502:physiology; D007546:Isoquinolines; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D013493:Suprachiasmatic Nucleus / Q000502:physiology*
chemical_list: D002712:Chlorides; D007473:Ion Channels; D007546:Isoquinolines; C017475:lucifer yellow