Thalamocortical dysrhythmia and the thalamic reticular nucleus in behaving rats.
OBJECTIVE
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 12-24h post-injection: potentiation of theta waves and spontaneous high-voltage spindles (HVS) at 4.5-8Hz 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.
Marini
G
G
INB, C.N.R., 20090 Segrate, Milano, Italy. gabriella.marini@unimi.it
Ceccarelli
P
P
Mancia
M
M
D000778:Anesthetics, Dissociative / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004576:Electromyography; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D007839:Functional Laterality / Q000502:physiology; D007051:Ibotenic Acid / Q000633:toxicity; D007649:Ketamine / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D017207:Rats, Sprague-Dawley; D013787:Thalamic Nuclei / Q000502:physiology*; D013788:Thalamus / Q000502:physiology*; D013826:Theta Rhythm / Q000187:drug effects
D000778:Anesthetics, Dissociative; D018690:Excitatory Amino Acid Agonists; D007051:Ibotenic Acid; D007649:Ketamine