High-speed visualization of calcium mediated sub-threshold oscillations in the parafascicular nucleus [842.06/B32]

HYDE JR; URBANO FJ; GARCIA-RILL E

New Orleans, LA, USA

Congreso; 2012 Society for Neuroscience Meeting.; 2012

Society for Neuroscience

The parafascicular nucleus (Pf) is an ascending target of the pedunculopontine nucleus (PPN) and is part of the ?non-specific? intralaminar thalamus modulating arousal. The PPN is involved in waking and REM sleep. Cortical EEG during these periods shows gamma band activity (~30-80Hz). In vitro, gamma oscillations are evident in all Pf neurons and are mediated by high threshold voltage-dependent P/Q- and N- type calcium channels. These studies tested the hypothesis that calcium sensitive dyes can be used to visualize sub-threshold calcium oscillations and that these visual recordings match electrical oscillations recorded using whole cell patch clamp. Electrical responses were recorded using whole cell patch clamp electrodes using 9-18 day old sagittal rat brain slices. Slices were recorded at 37°C while perfused with oxygenated aCSF in an immersion chamber containing synaptic blockers: APV, CNQX, Gabazine, Strychnine, and Tetrodotoxin. Recording electrodes also contained Fura-2, Indo-1, or Fluo-4 calcium sensitive dye. Cadmium was added to the aCSF to block voltage sensitive calcium channels as a control. The dendrites were visualized using a high speed, dual camera imaging system (Evolve 128, Photometrics). Calcium-mediated imaging recordings in the proximal dendrites showed a marked increase in activity as Pf neurons were depolarized using ramps. This occurred using all fluorescent calcium labels. Spectral power analysis of the electrical and calcium recordings showed time-coinciding peaks in both signals. The increase in calcium signal and the ramp-induced oscillations disappeared with the addition of cadmium. Cadmium also abolished the peaks in both the power spectra of both signals. Overlaying calcium and electrical recordings showed highly coincident oscillation peaks. Preliminary data suggests the presence of distributed oscillatory sub-domains. Each domain oscillates with a local phase and timing while the oscillations seen in electrical recordings in the soma are an average of the activity in all sub-domains. This study shows that high-speed calcium imaging is a viable method for measuring sub-threshold calcium oscillations with high spatial and temporal resolution. Support: NIH Grant R01 NS020246, NIH Grant P20 GM103425, FONCyT BID 1728 OC.AR, FONCyT PICT 2007-1009, FONCyT PICT 2008-2019.