Histological Verification of Ventral Lateral (VL) and Ventral Medial (VM) Thalamic Nuclei following Cerebellar Transcranial Electrical Stimulation (tES) in a Rat Model
Location
Suwanee, GA
Start Date
7-5-2024 1:00 PM
End Date
7-5-2024 4:00 PM
Description
Previous investigations have revealed that cerebellar tES can significantly influence inhibitory signals from ventrolateral (VL) and ventromedial (VL) thalamic localities in single electrode studies. The VL and VM nuclei receive input from the cerebellum and send efferent fibers to discrete, functionally distinct regions of the motor cortex. It is therefore reasonable to suspect that VM and VL could produce characteristically different outputs in response to tES, measured terminally as local field potential (LFP) in the motor cortex. Therefore it is reasonable to hypothesize that the variable depths of recording at these nuclei are correlated with changes in measured neuronal activities. To correlate the recording electrode depth to the thalamic neuronal activities, histology was utilized to verify the recording sites. Due to established differences in the arborization patterns of VL and VM projecting toward the motor cortex, it would be beneficial to characterize the relationship between electrode depth and electrophysiological output. A lesion was generated after the thalamic recordings by discharging a current (200 µA for 2 minutes). The brain was extracted and fixed in successive solutions of 15% and 30% sucrose in 4% paraformaldehyde for several days. The brain was subsequently trimmed to size, embedded in Tissue-Tek OCT embedding medium and chilled to -20℃. Trimmed tissues were sectioned at 20 μm on a CryoStar NX50, mounted and dried in room temperature and coverslipped with Permount Toluene Solution. This procedure was performed for both coronal and sagittal planes. Sections were stained in Cresyl Violet. Photomicrographs were collected to demonstrate the penetration in relationship with VL and VM. Recorded depths of target subnuclei in thalamus (5.55 mm and 6.6 mm for VL and VM respectively) were confirmed by histology. The two cells recorded at these depths demonstrated pre-stimulation firing rates of 1.15 Hz and 1.85 Hz for VL and VM respectively. These nuclei experienced subsequent decreases in net firing rate following tES (-0.03 Hz and -0.72 Hz for VL and VM respectively). In total, 5 recordings were obtained from VM and 7 recordings from VL over the course of experimentation. Future studies will incorporate additional recordings collected from VM and VL, confirmed by histology, with subsequent analysis to better define the electrophysiological profile of these two nuclei.
Embargo Period
5-23-2024
Histological Verification of Ventral Lateral (VL) and Ventral Medial (VM) Thalamic Nuclei following Cerebellar Transcranial Electrical Stimulation (tES) in a Rat Model
Suwanee, GA
Previous investigations have revealed that cerebellar tES can significantly influence inhibitory signals from ventrolateral (VL) and ventromedial (VL) thalamic localities in single electrode studies. The VL and VM nuclei receive input from the cerebellum and send efferent fibers to discrete, functionally distinct regions of the motor cortex. It is therefore reasonable to suspect that VM and VL could produce characteristically different outputs in response to tES, measured terminally as local field potential (LFP) in the motor cortex. Therefore it is reasonable to hypothesize that the variable depths of recording at these nuclei are correlated with changes in measured neuronal activities. To correlate the recording electrode depth to the thalamic neuronal activities, histology was utilized to verify the recording sites. Due to established differences in the arborization patterns of VL and VM projecting toward the motor cortex, it would be beneficial to characterize the relationship between electrode depth and electrophysiological output. A lesion was generated after the thalamic recordings by discharging a current (200 µA for 2 minutes). The brain was extracted and fixed in successive solutions of 15% and 30% sucrose in 4% paraformaldehyde for several days. The brain was subsequently trimmed to size, embedded in Tissue-Tek OCT embedding medium and chilled to -20℃. Trimmed tissues were sectioned at 20 μm on a CryoStar NX50, mounted and dried in room temperature and coverslipped with Permount Toluene Solution. This procedure was performed for both coronal and sagittal planes. Sections were stained in Cresyl Violet. Photomicrographs were collected to demonstrate the penetration in relationship with VL and VM. Recorded depths of target subnuclei in thalamus (5.55 mm and 6.6 mm for VL and VM respectively) were confirmed by histology. The two cells recorded at these depths demonstrated pre-stimulation firing rates of 1.15 Hz and 1.85 Hz for VL and VM respectively. These nuclei experienced subsequent decreases in net firing rate following tES (-0.03 Hz and -0.72 Hz for VL and VM respectively). In total, 5 recordings were obtained from VM and 7 recordings from VL over the course of experimentation. Future studies will incorporate additional recordings collected from VM and VL, confirmed by histology, with subsequent analysis to better define the electrophysiological profile of these two nuclei.