Key questions about the thalamus are still unanswered in part because of the inability to stimulate its inputs while monitoring cortical output. To address this, we employed flavoprotein autofluorescence optical imaging to expedite the process of developing a brain slice in mouse with connectivity among the auditory midbrain, thalamus, thalamic reticular nucleus, and cortex. Optical, electrophysiological, anatomic, and pharmacological tools revealed ascending connectivity from midbrain to thalamus and thalamus to cortex as well as descending connectivity from cortex to thalamus and midbrain and from thalamus to midbrain. The slices were relatively thick (600-700 μm), but, based on typical measures of cell health (resting membrane potential, spike height, and input resistance) and use of 2,3,5-triphenyltetrazolium chloride staining, the slices were as viable as thinner slices. As expected, after electrical stimulation of the midbrain, the latency of synaptic responses gradually increased from thalamus to cortex, and spiking responses were seen in thalamic neurons. Therefore, for the first time, it will be possible to manipulate and record simultaneously the activity of most of the key brain structures that are synaptically connected to the thalamus. The details for the construction of such slices are described herein.
Keywords: auditory; cortex; inferior colliculus; slice; thalamus.