Intrinsic spontaneous activity and subthreshold oscillations in neurones of the rat dorsal column nuclei in culture

Abstract

The basis of rhythmic activity observed at the dorsal column nuclei (DCN) is still open to debate. This study has investigated the electrophysiological properties of isolated DCN neurones deprived of any synaptic influence, using the perforated-patch technique. About half of the DCN neurones (64/130) were spontaneously active. More than half of the spontaneous neurones (36/64) showed a low threshold membrane oscillation (LTO) with a mean frequency of 11.4 Hz (range: 4.3-22.1 Hz, n = 20; I = 0). Cells showing LTOs also invariably showed a rhythmic 1.2 Hz clustering activity (groups of 2-5 action potentials separated by silent LTO periods). Also, more than one-third of the silent neurones presented clustering activity, always accompanied by LTOs, when slightly depolarised. The frequency of LTOs was voltage dependent and could be abolished by TTX (0.5 microM) and riluzole (30 microM), suggesting the participation of a sodium current. LTOs were also abolished by TEA (15 mM), which transformed clustering into tonic activity. In voltage clamp, most DCN neurones (85%) showed a TTX-/riluzole-sensitive persistent sodium current (INa,p), which activated at about -60 mV and had a half-maximum activation at -49.8 mV. An M-like, non-inactivating outward current was present in 95% of DCN neurones, and TEA (15 mM) inhibited this current by 73.7 %. The non-inactivating outward current was also inhibited by barium (1 mM) and linopirdine (10 microM), which suggests its M-like nature; both drugs failed to block the LTOs, but induced a reduction in their frequency by 56 and 20%, respectively. These results demonstrate for the first time that DCN neurones have a complex and intrinsically driven clustering discharge pattern, accompanied by subthreshold membrane oscillations. Subthreshold oscillations rely on the interplay of a persistent sodium current and a non-inactivating TEA-sensitive outward current.

Unraveling Cell Processes: Interference Imaging Interwoven with Data Analysis

“…and possibly also from cytoskeleton reorganization. In addition, spontaneous bursting activity of neurons may contribute to these rhythms [46]. Figure 7 shows spectral properties of RI dynamics in the membrane region (a, b), center (c, d) and nucleus region (e, f) of a mast cell.…”

Activation of TREK Currents by the Neuroprotective Agent Riluzole in Mouse Sympathetic Neurons

“…Riluzole inhibits voltage-activated sodium channels (Hebert et al, 1994;Reboreda et al, 2003;Wang et al, 2008), as reflected by the inhibition of transient and persistent sodium currents in cultured mSCG neurons (Lamas et al, 2009). As inhibition of a persistent sodium current would induce an apparent outward current, negative 15 mV voltage steps of 50 ms were applied at 0.4 Hz to track the variations in conductance induced by riluzole.…”

Interference Microscopy under Double-Wavelet Analysis: A New Approach to Studying Cell Dynamics

“…This is likely to be the result of a superposition of many membrane and cytoplasmic processes. We suppose that peaks at 10 -20 Hz correspond to the (i) spontaneous bursting activity of neurons [14] and (ii) movements of vesicles and organelles in the cytoplasm. The last assumption is in accordance with experimental data on frequencies of vesicle movements in neurons (8-40 Hz) obtained by light scattering measurements [15].…”