Rhythmic dendritic Ca2+ oscillations in thalamocortical neurons during slow non-REM sleep-related activity in vitro.
The distribution of T-type Ca2+ channels along the entire somatodendritic axis of sensory thalamocortical (TC) neurons permits regenerative propagation of low threshold spikes (LTS) accompanied by global dendritic Ca2+ influx. Furthermore, T-type Ca2+ channels play an integral role in low frequency oscillatory activity (<1–4 Hz) that is a defining feature of TC neurons. Nonetheless, the dynamics of T-type Ca2+ channel-dependent dendritic Ca2+ signalling during slow sleep-associated oscillations remains unknown. Here we demonstrate using patch clamp recording and two-photon Ca2+ imaging of dendrites from cat TC neurons undergoing spontaneous slow oscillatory activity that somatically recorded δ (1–4 Hz) and slow (<1 Hz) oscillations are associated with rhythmic and sustained global oscillations in dendritic Ca2+. In addition, our data reveal the presence of LTS-dependent Ca2+ transients (Δ[Ca2+]) in dendritic spine-like structures on proximal TC neuron dendrites during slow (<1 Hz) oscillations whose amplitudes are similar to those observed in the dendritic shaft. We find that the amplitude of oscillation associated Δ[Ca2+] do not vary significantly with distance from the soma whereas the decay time constant (τdecay) of Δ[Ca2+] decreases significantly in more distal dendrites. Furthermore, τdecay of dendritic Δ[Ca2+] increases significantly as oscillation frequency decreases from δ to slow frequencies where pronounced depolarised UP states are observed. Such rhythmic dendritic Ca2+ entry in TC neurons during sleep-related firing patterns could be an important factor in maintaining the oscillatory activity and associated biochemical signalling processes, such as synaptic downscaling, that occur in non-REM sleep.
A. C. Errington: Neuroscience Division, School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3AX, UK. erringtonac@cardiff.ac.uk
Adam C
AC
Errington
Stuart W
SW
Hughes
Vincenzo
V
Crunelli
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002415:Cats; D002540:Cerebral Cortex / Q000166:cytology*; D003713:Dendritic Cells / Q000378:metabolism*; D018613:Microscopy, Confocal; D012890:Sleep / Q000502:physiology*; D013788:Thalamus / Q000166:cytology*; D046509:Tissue Culture Techniques
D002118:Calcium