Optical imaging of thalamocortical activation in vitro

URBANO, FJ, LEZNIK, E & LLINÁS, RR.

San Diego, USA.

Congreso; 31st Annual Meeting of the Society for Neuroscience.; 2001

Society for Neuroscience

.Spatiotemporal properties of thalamocortical and corticothalamic loops were studied in vitro using optical imaging of voltage-sensitive dye signals combined with field potentials and intracellular recordings. Optical recordings were implemented in thalamocortical slices (400-450 <!--[if !vml]--><!--[endif]-->m thick) from 10-21 days old mice. The slices were stained with a voltage-sensitive dye RH-795 (Molecular Probes). Fluorescent activity was recorded using a fast CCD camera (Fujix HRDeltaron 1700) with 128x128 pixels of spatial resolution and 0.6 ms of temporal resolution. Specific (Ventrobasal) or unspecific (Medial and intralaminar) thalamic nuclei were stimulated with either single pulses or trains of stimuli using concentric bipolar electrodes. In the presence of dye, both specific and unspecific thalamic nuclei stimulation with low (2-10Hz) and high frequencies (30-50 Hz) trains were able to activate the thalamic reticular nucleus followed by neostriatum and specific cortical layers. Repetitive stimulation at high but not low frequencies was able to facilitate cortical signals. Stimulation of deep cortical layers resulted in the activation of the corresponding thalamic nuclei. The synaptic delays calculated using both electrophysiological and optical responses were similar. Nissl staining of the slices was performed to determine boundaries of the activated cortical layer. These results suggest the usefulness of thalamocortical slices in studying the physiology of specific and unspecific thalamocortical interactions and the dynamic properties of corticothalamic loops.Supported by: NIH-NINDS grant NS13742