Thalamocortical dysrhythmia and the thalamic reticular nucleus in behaving rats

• Published in: Clinical neurophysiology 2002-07, Vol.113 (7), p.1152-1164
• Main Authors: Marini, G, Ceccarelli, P, Mancia, M
• Format: Article
• Language: English
• Subjects: Anesthetics, Dissociative - pharmacology; Animals; Behavior, Animal - physiology; Biological and medical sciences; Brain Mapping; Cerebral Cortex - physiology; Electrodes, Implanted; Electroencephalogram; Electroencephalography; Electromyography; Excitatory Amino Acid Agonists - toxicity; Functional Laterality - physiology; Fundamental and applied biological sciences. Psychology; High-voltage spindles; Ibotenic acid; Ibotenic Acid - toxicity; Ketamine - pharmacology; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Rat; Rats; Rats, Inbred F344; Rats, Sprague-Dawley; Thalamic Nuclei - physiology; Thalamic reticular nucleus; Thalamus - physiology; Theta Rhythm - drug effects; Vertebrates: nervous system and sense organs
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/S1388-2457(02)00111-6

Objectives: The aim of this study was to investigate the effects of bilateral chemical lesion of the rostral pole of the thalamic reticular nucleus on EEG activities in freely moving rats applying quantitative analysis and brain mapping of power spectra distribution. Methods: Ketamine-sedated Sprague–Dawley rats were implanted to monitor behavioral states with frontoparietal electrodes in a first series of experiments and with multiple electrodes along the antero-posterior axis (F1, F2, F7, F8, T3, T4, P3, P4) in a second series. Monopolar and bipolar recordings were obtained in animals stereotaxically injected with ibotenic acid into both rostral poles of the thalamic reticular nucleus. Long-term video-EEG recordings and brain mapping based on quantitative spectral analysis were made. Results: Two forms of dysrhythmia gradually emerged in the neocortical EEG at 12–24 h post-injection: potentiation of theta waves and spontaneous high-voltage spindles (HVS) at 4.5–8 Hz frequency. Brain mapping during these dysrhythmia shows highest power posteriorly (parietotemporal) for theta and mesiofrontally for HVS. Conclusions: Given the lack of inhibitory intrinsic interneurons in the rat thalamus, bilateral destruction of a small part of the solely GABAergic population may promote cortical dysrhythmia (probably by dis-inhibition). The topographic differences in power might indicate different involved structures.